Applying Scientific Notation to Solve Problems

In April 2014, the population of the United States was about 308,000,000 people. The national debt was about $17,547,000,000,000. Write each number in scientific notation, rounding figures to two decimal places, and find the amount of the debt per U.S. citizen. Write the answer in both scientific and standard notations.

Solution

The population was $308,000,000 = 3.08\times 10^8$

The national debt was \ 17,547,000,000,000 \approx $ 1.75\times 10^13$

To find the amount of debt per citizen, divide the national debt by the number of citizens.

$$\begin{align*} (1.75\times 10^{13})\div (3.08\times 10^8) &= \Big(\frac{1.75}{3.08}\Big) \cdot \Bigg(\frac{10^{13}}{10^8} \Bigg) \\ &\approx 0.57 \times 10^5 \\ &= 5.7 \times 10^4 \end{align*}$$

The debt per citizen at the time was about \ 5.7\times 10^4$or$$57,000$.

Case

The above case, including the title and solution, is attributed to College Algebra 2e. Page 36.

Q&A

What are natural numbers?

Page 8, College Algebra 2e

The numbers we use for counting, or enumerating items, are the natural numbers: $1, 2, 3, 4, 5,$ and so on. We describe them in set notation as $\{1,2,3,\mathellipsis\}$ where the ellipsis $(\mathellipsis)$ indicates that the numbers continue to infinity. The natural numbers are, of course, also called the counting numbers. Any time we enumerate the members of a team, count the coins in a collection, or tally the trees in a grove, we are using the set of natural numbers.

What are the set of whole numbers?

Page 8, College Algebra 2e

The set of whole numbers is the set of natural numbers plus zero: $\{0,1,2,3,\mathellipsis\}$ .

What are the set of integers?

Page 8, College Algebra 2e

The set of integers adds the opposites of the natural numbers to the set of whole numbers: $\{\mathellipsis,-3,-2,-1,0,1,2,3,\mathellipsis\}$ . It is useful to note that the set of integers is made up of three distinct subsets: negative integers, zero, and positive integers. In this sense, the positive integers are just the natural numbers. Another way to think about it is that the natural numbers are a subset of the integers.

$\stackrel{\text{negative integers}}{\mathellipsis,-3,-2,-1} \quad \stackrel{\text{zero}}{0} \quad \stackrel{\text{positive integers}}{1,2,3,\mathellipsis}$

What are the set of rational numbers?

Page 8, College Algebra 2e

The set of rational numbers is written as $\{\frac{m}{n} \text{ | } m \text{ and } n \text{ are integers and } n \not = 0 \}$ . Notice from the definition that rational numbers are fractions (or quotients) containing integers in both the numerator and the denominator, and the denominator is never 0. We can also see that every natural number, whole number, and integer is a rational number with a denominator of 1.

Because they are fractions, any rational number can also be expressed in decimal form. Any rational number can be represented as either:

• a terminating decimal:$\frac{15}{8} = 1.875$, or
• a repeating decimal: $\frac{4}{11} = 0.36363636\mathellipsis=0.\overline{36}$

We use a line drawn over the repeating block of numbers instead of writing the group multiple times.

What are irrational numbers?

Page 9, College Algebra 2e

At some point in the ancient past, someone discovered that not all numbers are rational numbers. A builder, for instance, may have found that the diagonal of a square with unit sides was not 2 or even $\frac{3}{2}$ but was something else. Or a garment maker might have observed that the ratio of the circumference to the diameter of a roll of cloth was a little bit more than 3, but still not a rational number. Such numbers are said to be irrational because they cannot be written as fractions. These numbers make up the set of irrational numbers. Irrational numbers cannot be expressed as a fraction of two integers. It is impossible to describe this set of numbers by a single rule except to say that a number is irrational if it is not rational. So we write this as shown. $\{h \text{ | } h \text{ is not a rational number}\}$

What are real numbers?

Page 10, College Algebra 2e

Given any number n, we know that n is either rational or irrational. It cannot be both. The sets of rational and irrational numbers together make up the set of real numbers. As we saw with integers, the real numbers can be divided into three subsets: negative real numbers, zero, and positive real numbers. Each subset includes fractions, decimals, and irrational numbers according to their algebraic sign (+ or –). Zero is considered neither positive nor negative.

The real numbers can be visualized on a horizontal number line with an arbitrary point chosen as 0, with negative numbers to the left of 0 and positive numbers to the right of 0. A fixed unit distance is then used to mark off each integer (or other basic value) on either side of 0. Any real number corresponds to a unique position on the number line.The converse is also true: Each location on the number line corresponds to exactly one real number. This is known as a one- to-one correspondence. We refer to this as the real number line as shown in Figure 1.

What are order of operations?

Page 12-13, College Algebra 2e

Operations in mathematical expressions must be evaluated in a systematic order, which can be simplified using the acronym PEMDAS:

• P(arentheses)
• E(xponents)
• M(ultiplication) and D(ivision)
• A(ddition) and S(ubtraction)

What are commutative properties?

Page 14, College Algebra 2e

The commutative property of addition states that numbers may be added in any order without affecting the sum. $a+b=b+a$

We can better see this relationship when using real numbers. $(-2)+7=5 \quad \text{and} \quad 7+(-2)=5$

Similarly, the commutative property of multiplication states that numbers may be multiplied in any order without affecting the product. $a \cdot b=b \cdot a$

Again, consider an example with real numbers. $(-11)\cdot(-4)=44 \quad \text{and} \quad (-4)\cdot(-11)=44$

It is important to note that neither subtraction nor division is commutative. For example, $17-5$ is not the same as $5-17$ Similarly, $20\div5 \not = 5\div20$.

What are associative properties?

Page 14-15, College Algebra 2e

The associative property of multiplication tells us that it does not matter how we group numbers when multiplying. We can move the grouping symbols to make the calculation easier, and the product remains the same. $a(bc)=(ab)c$

Consider this example. $(3\cdot4)\cdot5=60 \quad \text{and} \quad 3\cdot(4\cdot5)=60$

The associative property of addition tells us that numbers may be grouped differently without affecting the sum. $a+(b+c)=(a+b)+c$

This property can be especially helpful when dealing with negative integers. Consider this example. $[15+(-9)]+23=29 \quad \text{and} \quad 15+[(-9)+23]=29$

Are subtraction and division associative? Review these examples.

$$\begin{align*} {4} 8-(3-15) &\stackrel{?}{=} (8-3)-15 &\quad 64\div(8\div4) &\stackrel{?}{=} (64\div8)\div4 \\ 8-(-12) &= 5-15 &\quad 64\div2 &\stackrel{?}{=} 8\div4 \\ 20 &\not= -10 &\quad 32 &\not= 2 \end{align*}$$

As we can see, neither subtraction nor division is associative.

What are distributive properties?

Page 15, College Algebra 2e

The distributive property states that the product of a factor times a sum is the sum of the factor times each term in the sum. $a \cdot (b+c) = a \cdot b + a \cdot c$

This property combines both addition and multiplication (and is the only property to do so). Let us consider an example.

Note that 4 is outside the grouping symbols, so we distribute the 4 by multiplying it by 12, multiplying it by –7, and adding the products.

To be more precise when describing this property, we say that multiplication distributes over addition. The reverse is not true, as we can see in this example.

$$\begin{align*} 6+(3\cdot5) &\stackrel{?}{=} (6+3)\cdot(6+5) \\ 6+(15) &\stackrel{?}{=} (9)\cdot(11) \\ 21 &\not= 99 \end{align*}$$

A special case of the distributive property occurs when a sum of terms is subtracted. $a-b=a+(-b)$

For example, consider the difference $12-(5+3)$. We can rewrite the difference of the two terms $12$ and $(5+3)$ by turning the subtraction expression into addition of the opposite. So instead of subtracting $(5+3)$ we add the opposite. $12+(-1)\cdot(5+3)$

Now, distribute $-1$ and simplify the result.

$$\begin{align*} 12-(5+3) &= 12+(-1)\cdot(5+3) \\ &= 12+[(-1)\cdot5+(-1)\cdot3] \\ &= 12+(-8) \\ &= 4 \end{align*}$$

This seems like a lot of trouble for a simple sum, but it illustrates a powerful result that will be useful once we introduce algebraic terms. To subtract a sum of terms, change the sign of each term and add the results. With this in mind, we can rewrite the last example.

$$\begin{align*} 12-(5+3) &= 12+(-5-3) \\ &= 12+(-8) \\ &= 4 \end{align*}$$

What are identity properties?

Page 15, College Algebra 2e

The identity property of addition states that there is a unique number, called the additive identity (0) that, when added to a number, results in the original number. $a+0=a$

The identity property of multiplication states that there is a unique number, called the multiplicative identity (1) that, when multiplied by a number, results in the original number. $a\cdot1=a$

For example, we have $(-6)+0=-6$ and $23\cdot1=23$. There are no exceptions for these properties; they work for every real number, including $0$ and $1$.

What are inverse properties?

Page 16, College Algebra 2e

The inverse property of addition states that, for every real number a, there is a unique number, called the additive inverse (or opposite), denoted by $(−a)$, that, when added to the original number, results in the additive identity, $0$. $a+(-a)=0$

For example, if $a=-8$, the additive inverse is $8$, since $(-8)+8=0$.

The inverse property of multiplication holds for all real numbers except $0$ because the reciprocal of $0$ is not defined. The property states that, for every real number a, there is a unique number, called the multiplicative inverse (or reciprocal), denoted $\frac{1}{a}$, that, when multiplied by the original number, results in the multiplicative identity, $1$. $a\cdot\frac{1}{a}=1$

For example, if $a=-\frac{2}{3}$, the reciprocal, denoted $\frac{1}{a}$, is $\frac{3}{2}$ because $a\cdot\frac{1}{a}=\Big(-\frac{2}{3}\Big)\cdot\Big(-\frac{3}{2}\Big)=1$

What are properties of real numbers?

Page 16, College Algebra 2e

The following properties hold for real numbers a, b, and c.

	Addition	Multiplication
Commutative Property	$a+b=b+a$	$a \cdot b=b \cdot a$
Associative Property	$a+(b+c)=(a+b)+c$	$a(bc)=(ab)c$
Distributive Property	$a\cdot(b+c)=a \cdot b+a \cdot c$	$a\cdot(b+c)=a \cdot b+a \cdot c$
Identity Property	There exists a unique real number called the additive identity, $0$, such that, for any real number $a$ $a+0=a$	There exists a unique real number called the multiplicative identity, $1$, such that, for any real number $a$ $a\cdot1=a$
Inverse Property	Every real number $a$ has an additive inverse, or opposite, denoted $-a$, such that $a+(-a)=0$	Every nonzero real number $a$ has a multiplicative inverse, or reciprocal, denoted $\frac{1}{a}$, such that $a \cdot \Big(\frac{1}{a}\Big)=1$

Evaluating Algebraic Expressions

Page 17, College Algebra 2e

So far, the mathematical expressions we have seen have involved real numbers only. In mathematics, we may see expressions such as $x+5,\frac{4}{3} \pi r^3$, or $\sqrt{2m^3n^2}$ . In the expression $x+5$, $5$ is called a constant because it does not vary and x is called a variable because it does. (In naming the variable, ignore any exponents or radicals containing the variable.) An algebraic expression is a collection of constants and variables joined together by the algebraic operations of addition, subtraction, multiplication, and division.

We have already seen some real number examples of exponential notation, a shorthand method of writing products of the same factor. When variables are used, the constants and variables are treated the same way.

$$\begin{align*} {3} (-3)^5 &= (-3)\cdot(-3)\cdot(-3)\cdot(-3)\cdot(-3) &\quad x^5 &= x \cdot x \cdot x \cdot x \cdot x \\ (2\cdot7)^3 &= (2\cdot7) \cdot (2\cdot7) \cdot (2\cdot7) &\quad (yz)^3 &= (yz)\cdot(yz)\cdot(yz) \\ \end{align*}$$

In each case, the exponent tells us how many factors of the base to use, whether the base consists of constants or variables.

Any variable in an algebraic expression may take on or be assigned different values. When that happens, the value of the algebraic expression changes. To evaluate an algebraic expression means to determine the value of the expression for a given value of each variable in the expression. Replace each variable in the expression with the given value, then simplify the resulting expression using the order of operations. If the algebraic expression contains more than one variable, replace each variable with its assigned value and simplify the expression as before.

What is an equation?

Page 19, College Algebra 2e

An equation is a mathematical statement indicating that two expressions are equal. The expressions can be numerical or algebraic. The equation is not inherently true or false, but only a proposition. The values that make the equation true, the solutions, are found using the properties of real numbers and other results. For example, the equation $2x+1=7$ has the solution $3$ because when we substitute $3$ for $x$ in the equation, we obtain the true statement $2(3)+1=7$.

What is a formula?

Page 19, College Algebra 2e

A formula is an equation expressing a relationship between constant and variable quantities. Very often, the equation is a means of finding the value of one quantity (often a single variable) in terms of another or other quantities. One of the most common examples is the formula for finding the area $A$ of a circle in terms of the radius $r$ of the circle: $A=\pi r^2$. For any value of $r$, the area $A$ can be found by evaluating the expression $\pi r^2$.

How is the product rule of exponents used?

Page 24, College Algebra 2e

Consider the product $x^3\cdot x^4$. Both terms have the same base, $x$, but they are raised to different exponents. Expand each expression, and then rewrite the resulting expression.

$$\begin{align*} x^3\cdot x^4 \enspace &= \enspace \stackrel{3 \text{ factors}}{x\cdot x\cdot x} \cdot \stackrel{4 \text{ factors}}{x\cdot x\cdot x\cdot x} \\ &= \enspace \stackrel{7 \text{ factors}}{x\cdot x\cdot x\cdot x\cdot x\cdot x\cdot x} \\ &= \enspace x^7 \end{align*}$$

The result is that $x^3\cdot x^{3+4} = x^7$.

Notice that the exponent of the product is the sum of the exponents of the terms. In other words, when multiplying exponential expressions with the same base, we write the result with the common base and add the exponents. This is the product rule of exponents.

$$a^m\cdot a^n = a^{m+n}$$

Now consider an example with real numbers.

$$2^3\cdot 2^4 = 2^{3+4} = 2^7$$

We can always check that this is true by simplifying each exponential expression. We find that $2^3$ is $8$, $2^4$ is $16$, and $2^7$ is $128$. The product $8\cdot 16$ equals $128$, so the relationship is true. We can use the product rule of exponents to simplify expressions that are a product of two numbers or expressions with the same base but different exponents.

How is the quotient rule of exponents used?

Page 25, College Algebra 2e

The quotient rule of exponents allows us to simplify an expression that divides two numbers with the same base but different exponents. In a similar way to the product rule, we can simplify an expression such as $\dfrac{y^m}{y^n}$, where $m>n$. Consider the example $\dfrac{y^9}{y^5}$. Perform the division by canceling common factors.

$$\begin{align*} \dfrac{y^9}{y^5} &= \dfrac{y\cdot y\cdot y\cdot y\cdot y\cdot y\cdot y\cdot y\cdot y}{y\cdot y\cdot y\cdot y\cdot y} \\ &= \dfrac{\cancel{y}\cdot \cancel{y}\cdot \cancel{y}\cdot \cancel{y}\cdot \cancel{y}\cdot y\cdot y\cdot y\cdot y}{\cancel{y}\cdot \cancel{y}\cdot \cancel{y}\cdot \cancel{y}\cdot \cancel{y}} \\ &= \dfrac{y\cdot y\cdot y\cdot y}{1} \\ &= y^4 \end{align*}$$

Notice that the exponent of the quotient is the difference between the exponents of the divisor and dividend.

$$\dfrac{a^m}{a^n} = a^{m-n}$$

In other words, when dividing exponential expressions with the same base, we write the result with the common base and subtract the exponents.

$$\dfrac{y^9}{y^5} = y^{9-5} = y^4$$

For the time being, we must be aware of the condition $m>n$. Otherwise, the difference $m-n$ could be zero or negative. Those possibilities will be explored shortly. Also, instead of qualifying variables as nonzero each time, we will simplify matters and assume from here on that all variables represent nonzero real numbers.

How is the power rule of exponents used?

Page 26, College Algebra 2e

Suppose an exponential expression is raised to some power. Can we simplify the result? Yes. To do this, we use the power rule of exponents. Consider the expression $\big(x^2\big)^3$. The expression inside the parentheses is multiplied twice because it has an exponent of $2$. Then the result is multiplied three times because the entire expression has an exponent of $3$.

$$\begin{align*} \big(x^2\big)^3 &= \stackrel{3 \text{ factors}}{(x^2)\cdot (x^2)\cdot (x^2)} \\ &= \stackrel{3 \text{ factors}}{\Big(\stackrel{2 \text{ factors}}{\overbrace{x\cdot x}}\Big)\cdot \Big(\stackrel{2 \text{ factors}}{\overbrace{x\cdot x}}\Big)\cdot \Big(\stackrel{2 \text{ factors}}{\overbrace{x\cdot x}}\Big)} \\ &= x\cdot x\cdot x\cdot x\cdot x\cdot x \\ &= x^6 \end{align*}$$

The exponent of the answer is the product of the exponents: $\big(x^2\big)^3 = x^{2\cdot 3} = x^6$. In other words, when raising an exponential expression to a power, we write the result with the common base and the product of the exponents.

$$\big(a^m\big)^n = a^{m\cdot n}$$

Be careful to distinguish between uses of the product rule and the power rule. When using the product rule, different terms with the same bases are raised to exponents. In this case, you add the exponents. When using the power rule, a term in exponential notation is raised to a power. In this case, you multiply the exponents.

$$\begin{gather*} \text{Product Rule} &\enspace &\enspace &\enspace \text{Power Rule} \\ \begin{align*} 5^3\cdot 5^4 &= 5^{3+4} &\enspace &= 5^7 \\ x^5\cdot x^2 &= x^{5+2} &\enspace &= x^7 \\ (3a)^7\cdot (3a)^{10} &= (3a)^{7+10} &\enspace &= (3a)^{17} \\ \end{align*} &\enspace &\text{but} &\enspace \begin{align*} (5^3)^4 &= 5^{3\cdot 4} &\enspace &= 5^{12} \\ (x^5)^2 &= x^{5\cdot 2} &\enspace &= x^{10} \\ ((3a)^7)^{10} &= (3a)^{7\cdot 10} &\enspace &= (3a)^{70} \\ \end{align*} \end{gather*}$$

How is the zero exponent rule of exponents used?

Page 26, College Algebra 2e

Return to the quotient rule. We made the condition that $m>n$ so that the difference $m-n$ would never be zero or negative. What would happen if $m=n$? In this case, we would use the zero exponent rule of exponents to simplify the expression to $1$. To see how this is done, let us begin with an example.

$$\begin{align*} \dfrac{t^8}{t^8} = \dfrac{\cancel{t^8}}{\cancel{t^8}} = 1 \end{align*}$$

If we were to simplify the original expression using the quotient rule, we would have

$$\dfrac{t^8}{t^8} = t^{8-8} = t^0$$

If we equate the two answers, the result is $t^0=1$. This is true for any nonzero real number, or any variable representing a real number.

$$a^0=1$$

The sole exception is the expression $0^0$. This appears later in more advanced courses, but for now, we will consider the value to be undefined.

How is the negative rule of exponents used?

Page 28-29, College Algebra 2e

Another useful result occurs if we relax the condition that $m > n$ in the quotient rule even further. For example, can we simplify $\frac{h^3}{h^5}$? When $m < n$ —that is, where the difference is negative—we can use the negative rule of exponents to simplify the expression to its reciprocal.

Divide one exponential expression by another with a larger exponent. Use our example, $\frac{h^3}{h^5}$.

$$\begin{align*} \dfrac{h^3}{h^5} &= \dfrac{h\cdot h\cdot h}{h\cdot h\cdot h\cdot h\cdot h} \\ &= \dfrac{\cancel{h}\cdot \cancel{h}\cdot \cancel{h}}{\cancel{h}\cdot \cancel{h}\cdot \cancel{h}\cdot h\cdot h} \\ &= \dfrac{1}{h\cdot h} \\ &= \dfrac{1}{h^2} \end{align*}$$

If we were to simplify the original expression using the quotient rule, we would have

$$\begin{align*} \dfrac{h^3}{h^5} &= h^{3-5} \\ &= h^{-2} \end{align*}$$

Putting the answers together, we have $h^{-2}=\frac{1}{h^2}$. This is true for any nonzero real number, or any variable representing a nonzero real number.

A factor with a negative exponent becomes the same factor with a positive exponent if it is moved across the fraction bar—from numerator to denominator or vice versa.

$$a^{-n}=\dfrac{1}{a^n} \enspace \text{and} \enspace a^n=\dfrac{1}{a^{-n}}$$

We have shown that the exponential expression $a^n$ is defined when $n$ is a natural number, $0$, or the negative of a natural number. That means that $a^n$ is defined for any integer $n$. Also, the product and quotient rules and all of the rules we will look at soon hold for any integer $n$.

How to find the power of a product?

Page 29-30, College Algebra 2e

To simplify the power of a product of two exponential expressions, we can use the power of a product rule of exponents, which breaks up the power of a product of factors into the product of the powers of the factors. For instance, consider $(pq^3)$. We begin by using the associative and commutative properties of multiplication to regroup the factors.

$$\begin{align*} (pq)^3 &= \stackrel{3 \text{ factors}}{(pq)\cdot (pq)\cdot (pq)} \\ &= p\cdot q\cdot p\cdot q\cdot q\cdot p\cdot q \\ &= \stackrel{3 \text{ factors}}{p\cdot p\cdot p}\cdot \stackrel{3 \text{ factors}}{q\cdot q\cdot q} \\ &= p^3\cdot q^3 \end{align*}$$

In other words, $(pq)^3 = p^3\cdot q^3$.

How to find the power of a quotient?

Page 30-31, College Algebra 2e

To simplify the power of a quotient of two expressions, we can use the power of a quotient rule, which states that the power of a quotient of factors is the quotient of the powers of the factors. For example, let’s look at the following example.

$$\big(e^{-2}f^2\big)^7 = \dfrac{f^{14}}{e^{14}}$$

Let’s rewrite the original problem differently and look at the result.

$$\begin{align*} \big(e^{-2}f^2\big)^7 &= \bigg(\frac{f^2}{e^2}\bigg)^7 \\ &= \dfrac{f^{14}}{e^{14}} \end{align*}$$

It appears from the last two steps that we can use the power of a product rule as a power of a quotient rule.

$$\begin{align*} \big(e^{-2}f^2\big)^7 &= \bigg(\frac{f^2}{e^2}\bigg)^7 \\ &= \dfrac{(f^2)^7}{(e^2)^7} \\ &= \dfrac{f^{2\cdot 7}}{e^{2\cdot 7}} \\ &= \dfrac{f^{14}}{e^{14}} \end{align*}$$

How to use scientific notation?

Page 32-33, College Algebra 2e

Recall at the beginning of the section that we found the number $1.3\times 10^{13}$ when describing bits of information in digital images. Other extreme numbers include the width of a human hair, which is about $0.00005 \text{m}$, and the radius of an electron, which is about $0.00000000000047 \text{m}$. How can we effectively work read, compare, and calculate with numbers such as these?

A shorthand method of writing very small and very large numbers is called scientific notation, in which we express numbers in terms of exponents of $10$. To write a number in scientific notation, move the decimal point to the right of the first digit in the number. Write the digits as a decimal number between $1$ and $10$. Count the number of places n that you moved the decimal point. Multiply the decimal number by $10$ raised to a power of $n$. If you moved the decimal left as in a very large number, is $n$ positive. If you moved the decimal right as in a small large number, $n$ is negative.

For example, consider the number $2,780,418$. Move the decimal left until it is to the right of the first nonzero digit, which is $2$.

We obtain $2.780418$ by moving the decimal point 6 places to the left. Therefore, the exponent of $10$ is $6$, and it is positive because we moved the decimal point to the left. This is what we should expect for a large number.

$$2.780418\times 10^6$$

Working with small numbers is similar. Take, for example, the radius of an electron, $0.00000000000047 \text{ m}$. Perform the same series of steps as above, except move the decimal point to the right.

Be careful not to include the leading $0$ in your count. We move the decimal point $13$ places to the right, so the exponent of $10$ is $13$. The exponent is negative because we moved the decimal point to the right. This is what we should expect for a small number.

$$4.7\times 10^{-13}$$

How to convert from scientific notation to standard notation?

Page 34, College Algebra 2e

To convert a number in scientific notation to standard notation, simply reverse the process. Move the decimal $n$ to the right if $n$ is positive or $n$ places to the left if $n$ is negative and add zeros as needed. Remember, if $n$ is positive, the value of the number is greater than $1$, and if $n$ is negative, the value of the number is less than one.

How to use scientific notation in applications?

Page 35, College Algebra 2e

Scientific notation, used with the rules of exponents, makes calculating with large or small numbers much easier than doing so using standard notation. For example, suppose we are asked to calculate the number of atoms in 1 L of water. Each water molecule contains 3 atoms (2 hydrogen and 1 oxygen). The average drop of water contains around $1.32\times 10^{21}$ molecules of water and 1 L of water holds about $1.22\times 10^4$ average drops. Therefore, there are approximately $3\cdot (1.32\times 10^{21})\cdot (1.22\times 10^4)\approx 4.83\times 10^{25}$ atoms in 1 L of water. We simply multiply the decimal terms and add the exponents. Imagine having to perform the calculation without using scientific notation!

When performing calculations with scientific notation, be sure to write the answer in proper scientific notation. For example, consider the product $(7\times 10^4)\cdot (5\times 10^6) = 35\times 10^{10}$. The answer is not in proper scientific notation because 35 is greater than 10. Consider 35 as $3.5\times 10$. That adds a ten to the exponent of the answer.

$$(35)\times 10^{10} = (3.5\times 10)\times 10^{10} = 3.5\times (10\times 10^{10}) = 3.5\times 10^{11}$$

Glossary

Associative Property

https://en.wikipedia.org/wiki/Associative_property

The associative property is a property of some binary operations, which means that rearranging the parentheses in an expression will not change the result.

Consider the following equations:

$$\begin{aligned} (2+3)+4 &= 2+(3+4) = 9 \\ 2\times (3\times 4) &= (2\times 3)\times 4 = 24 \end{aligned}$$

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January 01, 2024

Commutative Property

https://en.wikipedia.org/wiki/Commutative_property

A binary operation is commutative if changing the order of the operands does not change the result.

E.g. $3 + 4 = 4 + 3$ or $2 × 5 = 5 × 2$

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January 01, 2024

Decimal

https://en.wikipedia.org/wiki/Decimal

A decimal numeral (also often just decimal or, less correctly, decimal number), refers generally to the notation of a number in the decimal numeral system. Decimals may sometimes be identified by a decimal separator (usually "." or "," as in 25.9703 or 3,1415).

The decimal numeral system (also called the base-ten positional numeral system and denary /ˈdiːnəri/[1] or decanary) is the standard system for denoting integer and non-integer numbers.

Denominator

https://en.wiktionary.org/wiki/denominator

The number or expression written below the line in a fraction (such as 2 in ½).

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December 26, 2023

Distributive Property

https://en.wikipedia.org/wiki/Distributive_property

The distributive property of binary operations is a generalization of the distributive law, which asserts that the equality

$$x\cdot (y+z) = x\cdot y + x\cdot z$$

is always true in elementary algebra. For example, in elementary arithmetic, one has

$$2\cdot (1+3) = 2\cdot 1 + 2\cdot 3$$

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Equation

https://en.wikipedia.org/wiki/Equation

An equation is a mathematical formula that expresses the equality of two expressions, by connecting them with the equals sign $=$.

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January 01, 2024

Expression

https://en.wikipedia.org/wiki/Expression_(mathematics)

An expression or mathematical expression is a finite combination of symbols that is well-formed according to rules that depend on the context. Mathematical symbols can designate numbers (constants), variables, operations, functions, brackets, punctuation, and grouping to help determine order of operations and other aspects of logical syntax.

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January 01, 2024

Fraction

https://en.wikipedia.org/wiki/Fraction

A fraction represents a part of a whole or, more generally, any number of equal parts.

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December 26, 2023

Identity Property

https://simple.wikipedia.org/wiki/Identity_Property

In math, the identity property is made up of two parts: the additive identity property and the multiplicative identity property.

The additive identity property says that the sum of adding any number and zero (0) is just the original number. For that reason, zero is often called the additive identity of common numbers.

The multiplicative identity property says that the product of multiplying any number and one (1) is just the original number. Also, if you divide a number by itself, the result (quotient) is one. For that reason, one is often called the multiplicative identity of common numbers.

Last accessed

January 01, 2024

Integer

https://en.wikipedia.org/wiki/Integer

An integer is the number zero (0), a positive natural number (1, 2, 3, etc.) or a negative integer (−1, −2, −3, etc.).

Last accessed

December 26, 2023

Inverse Property

https://en.wikipedia.org/wiki/Additive_inverse

https://en.wikipedia.org/wiki/Multiplicative_inverse

The additive inverse of a number $a$(sometimes called the opposite of $a$) is the number that, when added to $a$, yields zero.

A multiplicative inverse or reciprocal for a number $x$, denoted by $\frac{1}{x}$ or $x^{−1}$, is a number which when multiplied by $x$ yields the multiplicative identity, $1$

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January 01, 2024

Irrational Number

https://en.wikipedia.org/wiki/Irrational_number

All the real numbers that are not rational numbers. That is, irrational numbers cannot be expressed as the ratio of two integers.

Among irrational numbers are the ratio $\pi$ of a circle's circumference to its diameter, Euler's number $e$, the golden ratio $\phi$, and the square root of two.[1] In fact, all square roots of natural numbers, other than of perfect squares, are irrational.

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January 01, 2024

Negative Rule of Exponents

Page 29, College Algebra 2e

For any nonzero real number $a$ and natural number $n$, the negative rule of exponents states that

$$a^{-n} = \dfrac{1}{a^n}$$

Numerator

https://en.wiktionary.org/wiki/numerator

The number or expression written above the line in a fraction (such as 1 in ½).

Last accessed

December 26, 2023

Order of Operations

https://en.wikipedia.org/wiki/Order_of_operations

The order of operations is a collection of rules that reflect conventions about which operations to perform first in order to evaluate a given mathematical expression.

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January 01, 2024

Perimeter

https://en.wikipedia.org/wiki/Perimeter

A perimeter is a closed path that encompasses, surrounds, or outlines either a two dimensional shape or a one-dimensional length. The perimeter of a circle or an ellipse is called its circumference.

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January 01, 2024

Power of a Product Rule of Exponents

Page 30, College Algebra 2e

For any real numbers $a$ and $b$ and any integer $n$, the power of a product rule of exponents states that

$$(ab)^n = a^nb^n$$

Power of a Quotient Rule of Exponents

Page 31, College Algebra 2e

For any real numbers $a$ and $b$ and any integer $n$, the power of a quotient rule of exponents states that

$$\bigg(\dfrac{a}{b}\bigg)^n = \dfrac{a^n}{b^n}$$

Power Rule of Exponents

Page 26, College Algebra 2e

For any real number $a$ and positive integers $m$ and $n$, the power rule of exponents states that

$$\big(a^m\big)^n = a^{m\cdot n}$$

Product Rule of Exponents

Page 24, College Algebra 2e

For any real number $a$ and natural numbers $m$ and $n$, the product rule of exponents states that

$$a^m\cdot a^n = a^{m+n}$$

Quotient Rule of Exponents

Page 25, College Algebra 2e

For any real number $a$ and natural numbers $m$ and $n$, the quotient rule of exponents states that

$$\dfrac{a^m}{a^n} = a^{m-n}$$

Rational Number

https://commons.wikimedia.org/wiki/Category:Rational_numbers

A rational number is any number that can be expressed as the quotient or fraction $\frac{p}{q}$ of two integers, with the denominator $q$ not equal to zero. Since $q$ may be equal to 1, every integer is a rational number. This category represents all rational numbers, that is, those real numbers which can be represented in the form: a b $\frac{a}{b}$ ...where $a$ and $b$ are integers and $b$ is not equal to zero. All integers are rational, including zero.

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December 26, 2023

Real Number

https://en.wikipedia.org/wiki/Real_number

The real numbers include the rational numbers, such as the integer −5 and the fraction 4 / 3. The rest of the real numbers are called irrational numbers.

Real numbers can be thought of as all points on a line called the number line or real line, where the points corresponding to integers (..., −2, −1, 0, 1, 2, ...) are equally spaced.

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January 01, 2024

Repeating Decimal

https://en.wikipedia.org/wiki/Repeating_decimal

A repeating decimal or recurring decimal is a decimal representation of a number whose digits are periodic (repeating its values at regular intervals) and the infinitely repeated portion is not zero. It can be shown that a number is rational if and only if its decimal representation is repeating or terminating (i.e. all except finitely many digits are zero). For example, the decimal representation of $\frac{1}{3}$ becomes periodic just after the decimal point, repeating the single digit "3" forever, i.e. 0.333.... A more complicated example is $\frac{3227}{555}$, whose decimal becomes periodic at the second digit following the decimal point and then repeats the sequence "144" forever, i.e. 5.8144144144.... At present, there is no single universally accepted notation or phrasing for repeating decimals. Another example of this is $\frac{593}{53}$, which becomes periodic after the decimal point, repeating the 13-digit pattern "1886792452830" forever, i.e. 11.18867924528301886792452830....

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January 01, 2024

Scientific Notation

Page 33, College Algebra 2e

A number is written in scientific notation if it is written in the form $a\times 10^n$, where $1\le |a| \lt 10$ and $n$ is an integer

Surface Area

https://en.wikipedia.org/wiki/Surface_area

The surface area (symbol A) of a solid object is a measure of the total area that the surface of the object occupies.

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January 01, 2024

Terminating Decimal

https://en.wikipedia.org/wiki/Decimal

A decimal that only has a finite number of digits after the decimal seperator.

Last accessed

January 01, 2024

Zero Exponent Rule of Exponents

Page 27, College Algebra 2e

For any nonzero real number $a$, the zero exponent rule of exponents states that

$$a^0 = 1$$

note

• Content last updated on January 01, 2024
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