PSAT Math : Operations with Fractions

Study concepts, example questions & explanations for PSAT Math

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Example Questions

Example Question #1 : Operations With Fractions

Evaluate the following:

Possible Answers:

\frac{25}{507}

\frac{507}{400}

None of the available answers

\frac{4}{5}

\frac{400}{507}

Correct answer:

\frac{400}{507}

Explanation:

First we will evaluate the terms in the parentheses:

Next, we will square the first fraction:

\frac{100}{169}\div \frac{3}{4}

We can evaluate the division as such:

\frac{100}{169}\times\frac{4}{3}=\frac{400}{507}

Example Question #2 : How To Divide Fractions

Simplify: 

Possible Answers:

Correct answer:

Explanation:

Start by rewriting this fraction as a division problem:

When dividing fractions, you multiply by the reciprocal of the second fraction, so you can rewrite your problem like this:

Multiply across the numerators and then across the denominators to get . The x's cancel, and you can reduce the fraction to be .

Example Question #3 : How To Divide Fractions

Define an operation  as follows:

For all real numbers ,

.

Evaluate .

Possible Answers:

Correct answer:

Explanation:

, or, equivalently,

Example Question #1 : How To Divide Fractions

Define an operation  as follows:

For all real numbers ,

.

Evaluate .

Possible Answers:

Correct answer:

Explanation:

,

or, equivalently, 

 

Example Question #5 : How To Divide Fractions

Define an operation  as follows:

For all real numbers ,

.

Evaluate .

Possible Answers:

Correct answer:

Explanation:

Example Question #111 : Fractions

Define an operation  as follows:

For all real numbers ,

.

Evaluate .

Possible Answers:

Correct answer:

Explanation:

Example Question #7 : How To Divide Fractions

Define an operation  as follows:

For all real numbers ,

.

Evaluate .

Possible Answers:

The correct answer is not among the other responses.

Correct answer:

Explanation:

or, equivalently,

Example Question #111 : Fractions

Define an operation  as follows:

For all real numbers ,

.

Evaluate .

Possible Answers:

Correct answer:

Explanation:

,

or, equivalently,

From here we need to find a common denominator.

 

 

Example Question #111 : Fractions

Simplify:

Possible Answers:

Correct answer:

Explanation:

Begin by simplifying any additions that need to be done:

becomes

Now, remember that the numerator  can be rewritten :

Now, when you divide fractions, you multiply the numerator by the reciprocal of the denominator:

Cancel the s and you get: 

Example Question #121 : Fractions

If xy = 1 and 0 < x < 1, then which of the following must be true?

Possible Answers:

y = 1

x

y = x

< 1

y > 1

Correct answer:

y > 1

Explanation:

If x is between 0 and 1, it must be a proper fraction (e.g., ½ or ¼). Solving the first equation for y, y = 1/x. When you divide 1 by a proper fraction between 0 and 1, the result is the reciprocal of that fraction, which will always be greater than 1.

To test this out, pick any fraction. Say x = ½. This makes y = 2.

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