Pre-Algebra : Operations

Study concepts, example questions & explanations for Pre-Algebra

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Example Questions

Example Question #361 : Operations

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

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

Possible Answers:

\(\displaystyle >\)

\(\displaystyle < \)

\(\displaystyle \leq\)

\(\displaystyle =\)

\(\displaystyle \geq\)

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 #362 : Operations

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

 

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

Possible Answers:

\(\displaystyle >\)

\(\displaystyle \leq\)

\(\displaystyle =\)

\(\displaystyle < \)

\(\displaystyle \geq\)

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 #363 : Operations

Simplify the following expression:

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

Possible Answers:

\(\displaystyle -6\)

\(\displaystyle -82\)

\(\displaystyle 6\)

\(\displaystyle 82\)

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 #364 : Operations

Simplify the following:

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

Possible Answers:

\(\displaystyle 18\)

\(\displaystyle 14\)

\(\displaystyle 22\)

\(\displaystyle 10\)

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 #365 : Operations

Solve for x in the following equation:

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

Possible Answers:

\(\displaystyle x = 9\)

\(\displaystyle x = 3\)

\(\displaystyle x = -12\)

\(\displaystyle x = 12\)

\(\displaystyle x = -3\)

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 #366 : Operations

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

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

Possible Answers:

\(\displaystyle < \)

\(\displaystyle \leq\)

\(\displaystyle =\)

\(\displaystyle \geq\)

\(\displaystyle >\)

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

\(\displaystyle 7 < 9\)

Example Question #367 : Operations

\(\displaystyle \left | -15 | + \left | 24 | = ?\)

Possible Answers:

\(\displaystyle -39\)

\(\displaystyle 9\)

\(\displaystyle 39\)

\(\displaystyle -9\)

Correct answer:

\(\displaystyle 39\)

Explanation:

The symbol | | around each real number signifies absolute value. Absolute value is the true magnitude of a real number, without looking at the positive or negative sign attached to it. To rewrite this problem when solving, remove all absolute value symbols as well as signs.

\(\displaystyle 15 + 24 = 39\)

Example Question #368 : Operations

Solve the following:

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

Possible Answers:

\(\displaystyle -8\)

\(\displaystyle -16\)

\(\displaystyle 48\)

\(\displaystyle 16\)

\(\displaystyle 8\)

Correct answer:

\(\displaystyle 16\)

Explanation:

The absolute value of a number is defined as the position or distance of the number from zero on the number.  Because it is a distance, the value cannot be negative.  So,

\(\displaystyle \left | -12\right | = 12\)

and

\(\displaystyle \left | -4\right | = 4\)

so

\(\displaystyle \left | -12\right | + \left | -4\right | = 12 + 4 = 16\)

Example Question #369 : Operations

If  \(\displaystyle x = 5\), what is the value of  \(\displaystyle |-18 - |x + 18 ||\)  ?

Possible Answers:

\(\displaystyle 5\)

\(\displaystyle 31\)

\(\displaystyle -31\)

\(\displaystyle -5\)

\(\displaystyle 41\)

Correct answer:

\(\displaystyle 41\)

Explanation:

Substitute 5 for \(\displaystyle x\) in the given equation and evaluate.

\(\displaystyle |-18 - |5+ 18 ||= |-18 - |23 ||\)

Remember that the absolute value of a number is its distance from zero on a number line. Distance is always positive; therefore, you can rewrite the expression.

\(\displaystyle |-18 - |23 ||= |-18 - 23|\)

Subtracting a positive number from a negative number is the same as adding a negative number. 

\(\displaystyle |-18 - 23|= |-18 +\left ( - 23 \right )|\)

\(\displaystyle |-18 +\left ( - 23 \right )|= |-\left (18 + 23 \right )|\)

\(\displaystyle |-\left (18 + 23 \right )|= |- 41|\)

Solve.

\(\displaystyle |- 41|= 41\)

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