Pre-Algebra : Absolute Value

Study concepts, example questions & explanations for Pre-Algebra

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Example Questions

Example Question #357 : Operations

Solve the absolute value:  \(\displaystyle \left |-6-6 \right |^{-2}\)

Possible Answers:

\(\displaystyle \frac{1}{24}\)

\(\displaystyle \frac{1}{144}\)

\(\displaystyle -\frac{1}{144}\)

\(\displaystyle -24\)

\(\displaystyle -12\)

Correct answer:

\(\displaystyle \frac{1}{144}\)

Explanation:

Solve the terms inside the absolute value first.

\(\displaystyle \left |-6-6 \right |^{-2} = \left | -12\right |^{-2}\)

Simplify the absolute value.  Any term inside the absolute value is converted to a positive value.

\(\displaystyle (12)^{-2}\)

Convert the negative exponent to a positive exponent by taking the reciprocal of the inner term.  Simplify.

\(\displaystyle (12)^{-2} = \frac{1}{12^2} = \frac{1}{144}\)

Example Question #352 : Operations And Properties

Solve the equation below.

\(\displaystyle \left | 3 * -5\right | + -2 =\)

Possible Answers:

\(\displaystyle 17\)

\(\displaystyle - 13\)

\(\displaystyle - 17\)

\(\displaystyle 13\)

\(\displaystyle 30\)

Correct answer:

\(\displaystyle 13\)

Explanation:

The straight brackets indicate absolute value.

Absolute value means the distance from zero.

Example: Even a -16 is still 16 away from zero.

Therefore, \(\displaystyle \left | 3 * -5\right | + - 2 =\)

\(\displaystyle \left | - 15\right | + - 2 =\)

The absolute value of -15 is 15.

\(\displaystyle 15 + -2 = 13\)

Example Question #356 : Operations

Solve the following equation.

\(\displaystyle \left | -7 \right | \cdot \left | 6\right |\)

Possible Answers:

\(\displaystyle -42\)

\(\displaystyle -56\)

\(\displaystyle 42\)

\(\displaystyle -13\)

\(\displaystyle 56\)

Correct answer:

\(\displaystyle 42\)

Explanation:

The absolute value of a number is its distance from zero on a number line. Because of that, the absolute value of a number can never be negative.

So,

\(\displaystyle \left | -7\right | = 7\)

because the distance from zero to -7 on a number line is 7.

So,

\(\displaystyle \left | -7 \right | \cdot \left | 6\right | = 7 \cdot 6 = 42\)

Example Question #357 : Operations

Solve:

\(\displaystyle \left | 8-15\right |\div -8\)

Possible Answers:

\(\displaystyle -\frac{23}{8}\)

\(\displaystyle \frac{7}{8}\)

None of the other answers

\(\displaystyle -\frac{7}{8}\)

\(\displaystyle \frac{23}{8}\)

Correct answer:

\(\displaystyle -\frac{7}{8}\)

Explanation:

First, we solve the absolute value portion:

\(\displaystyle \left | 8-15\right |\div -8\)

\(\displaystyle \left | -7\right |\div -8\)

\(\displaystyle 7\div -8\)

\(\displaystyle \frac{7}{-8}\)

\(\displaystyle -\frac{7}{8}\)

 

Example Question #361 : Operations

Fill in the blank using \(\displaystyle < , >, \leq, \geq, \text{or} =\).

\(\displaystyle \left | -9 \right | \square \ 4\)

Possible Answers:

\(\displaystyle >\)

\(\displaystyle \leq\)

\(\displaystyle < \)

\(\displaystyle \geq\)

\(\displaystyle =\)

Correct answer:

\(\displaystyle >\)

Explanation:

The term \(\displaystyle \left | -9\right |\) displays an absolute value.  Absolute value is defined as the distance of a number in relation to zero on a number line.  Since it is a distance, an absolute value cannot be negative.  So,

\(\displaystyle \left | -9\right | = 9\)

So, we can rewrite the orignal problem as

\(\displaystyle 9\ \square \ 4\)

and we can easily see that

\(\displaystyle 9 > 4\)

Example Question #42 : Absolute Value

Compare the following using \(\displaystyle < , >, \leq, \geq, =\)

 

\(\displaystyle \left | -18\right | \square \left | 18\right |\)

Possible Answers:

\(\displaystyle < \)

\(\displaystyle >\)

\(\displaystyle \geq\)

\(\displaystyle \leq\)

\(\displaystyle =\)

Correct answer:

\(\displaystyle =\)

Explanation:

The absolute value of a number is the distance that number is from zero on a number.  Because it is a distance, the absolute value can never be negative.  So,

\(\displaystyle \left | -18\right | \square \left | 18\right |\)

can be written as

\(\displaystyle 18 \ \square \ 18\)

Therefore, it's easy to solve.

\(\displaystyle 18 = 18\)

Example Question #43 : Absolute Value

Simplify the following expression:

\(\displaystyle \left | -44+38\right |\)

Possible Answers:

\(\displaystyle 82\)

\(\displaystyle -6\)

\(\displaystyle -82\)

\(\displaystyle 6\)

Correct answer:

\(\displaystyle 6\)

Explanation:

Simplify the following expression:

\(\displaystyle \left | -44+38\right |\)

Let's begin by focusing on the inside of the absolute value signs:

\(\displaystyle -44+38=-6\)

However, because we are within the absolute value signs, we need to change the negative sign to a positive one.

\(\displaystyle \left | -6\right |=6\)

Anytime you have something within the absolute value sign, you need to make it positive.

Our answer is 6.

Example Question #41 : Absolute Value

Simplify the following:

\(\displaystyle \left | -4\right |+4-\left | 2\right |+12\)

Possible Answers:

\(\displaystyle 22\)

\(\displaystyle 14\)

\(\displaystyle 18\)

\(\displaystyle 10\)

None of the above

Correct answer:

\(\displaystyle 18\)

Explanation:

It is important to be careful of where the negative sign is when simplifying.

When simplifying you should end up with:

\(\displaystyle 4+4-2+12\)  which equals  \(\displaystyle 18\)

Example Question #362 : Operations And Properties

Solve for x in the following equation:

\(\displaystyle 2x + \left | -9 \right | = 15\)

Possible Answers:

\(\displaystyle x = 9\)

\(\displaystyle x = 12\)

\(\displaystyle x = 3\)

\(\displaystyle x = -12\)

\(\displaystyle x = -3\)

Correct answer:

\(\displaystyle x = 3\)

Explanation:

The absolute value is defined as the distance that number is from zero on the number line.  Because it is a distance, the absolute value cannot be negative. So, in the equation

\(\displaystyle 2x + \left | -9 \right | = 15\)

we look at the absolute value.

\(\displaystyle \left | -9\right | = 9\)

because -9 is 9 units from zero.  Now, we can solve for x.

\(\displaystyle 2x + 9 = 15\)

\(\displaystyle 2x + 9 - 9 = 15 - 9\)

\(\displaystyle 2x = 6\)

\(\displaystyle \frac{2x}{2} = \frac{6}{2}\)

\(\displaystyle x = 3\)

Example Question #46 : Absolute Value

Compare the following using \(\displaystyle < , >, \leq, \geq, =\)

\(\displaystyle 7 \ \square \ \left | -9\right |\)

Possible Answers:

\(\displaystyle =\)

\(\displaystyle >\)

\(\displaystyle \leq\)

\(\displaystyle < \)

\(\displaystyle \geq\)

Correct answer:

\(\displaystyle < \)

Explanation:

Absolute values are defined as the distance the number is from zero on a number line.  Because it is a distance, the absolute value cannot be negative.  So,

\(\displaystyle \left | -9 \right | = 9\)

because -9 is 9 units from zero on a number line.  So,

\(\displaystyle 7 \ \square \ 9\)

can easily be solved as

\(\displaystyle 7 < 9\)

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