GRE Math : Fractions

Study concepts, example questions & explanations for GRE Math

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Example Questions

Example Question #1 : How To Find The Lowest / Least Common Denominator

In simplest form,  

Possible Answers:

Correct answer:

Explanation:

First, find the smallest number that both  and  will factor into, which is .

This means that the fist fraction should be multiplied by  and the second should be multiplied by .

Therefore,

 .

Then, add the numerators while the denomenators stay the same: 

.

Then, reduce the fraction to its lowest terms: 

.

Example Question #61 : Fractions

For how many integers, , between 26 and 36 is it true that

  and  are all in lowest terms?

Possible Answers:

Correct answer:

Explanation:

If  is even, then  is not in lowest terms, since both  and 4 are divisible by 2. Therefore, the only possibilities are 27,29,31,33, and 35. But , and , so only two integers satisfy the given condition: 29 and 31.

Example Question #1062 : Gre Quantitative Reasoning

Mrs. Lawrence's class has  students,  of which are girls.  If you were to choose a student at random, what's the probability that the student chosen would be a boy?

Possible Answers:

Correct answer:

Explanation:

In order to find out the probability of choosing a boy, you must first find out how many boys there are. Since there are  girls out of  students,  students should be boys.  

Therefore, the probability of choosing a boy is,

 .

 However, this is not one of the answer choices; therefore, you must reduce the fraction.  

In order to reduce a fraction, you have to find their GCM, or greatest common multiple. This is the biggest number that will go into both the numerator  and denominator .  The largest number is . Divide both the top and bottom by , and you will get the answer:

Example Question #1063 : Gre Quantitative Reasoning

Simplify the fraction:

Possible Answers:

Correct answer:

Explanation:

To simplify the fraction

It may be helpful to write it in terms of scientific notation:

 

Example Question #1064 : Gre Quantitative Reasoning

Simply the fraction:

Possible Answers:

Correct answer:

Explanation:

To simplify the fraction

Begin by factoring out common terms in the numerator and denominator:

Now notice that the coefficients for the polynomials in the numerator and denominator match the form of Pascal's Triangle:

The fraction can be rewritten as:

And finally reduced to

Example Question #1 : How To Find Out A Mixed Fraction From An Improper Fraction

 and  are positive integers.

 is a multiple of .

Quantity A:

Quantity B:

 

Possible Answers:

Quantity B is greater.

Quantity A is greater.

The two quantities are equal.

The relationship cannot be determined.

Correct answer:

The relationship cannot be determined.

Explanation:

Recall that the exponent of the denominator is sutracted from the exponent of the numerator. 

Therefore Quantity A is equivalent to x5–y, and because we would then be comparing an arithmetic operation to a geometric operation, it does not matter whether y is a multiple of 5.  The two quantities cannot be compared.

Example Question #1 : How To Find Out A Mixed Fraction From An Improper Fraction

Which of the following is the mixed fraction equivalent to ?

Possible Answers:

Correct answer:

Explanation:

To begin, notice that using your calculator, you can find:

Now, the closest even multiple of  that is less than  is .  Therefore, you know that your number is:

This is the same as:

, or simply, .  This is your mixed fraction.

Example Question #1 : Mixed / Improper Fractions

Which of the following is equivalent to ?

Possible Answers:

Correct answer:

Explanation:

Although there are many ways to convert improper fractions into mixed fractions, the easiest way is to use your calculator to your advantage.  Begin by dividing  by .  This gives you . Therefore, you can eliminate all the options that have do not have  for their first portion. Next, multiply  by the denominator (), and get .  This means that you have  and , or .  Thus, your answer is .

Example Question #2 : How To Find Out A Mixed Fraction From An Improper Fraction

Quantity A: 

Quantity B: 

Which of the following is true?

Possible Answers:

Quantity A is larger.

The relationship of the two quantities cannot be determined based on the information provided.

The two quantities are equal

Quantity B is larger.

Correct answer:

The two quantities are equal

Explanation:

Though there are several ways you could solve this, let's convert the improper fraction into a mixed one so we can compare them. Start by dividing  by .  This gives you  

Now, since we know that the two numbers have the same whole-number value, we need to compare their decimal portions. Compare  to . The latter is indeed   Therefore, the two values are equal.

Example Question #1 : Mixed / Improper Fractions

Write as an improper fraction.

 

Possible Answers:

Correct answer:

Explanation:

To find the improper fraction value, we must effectively add together 71 and 5/7. To do this, we will give 71 a denominator of 7; therefore, we are transforming 71/1 to x/7.  The shortest way to do this is to multiply by 7/7 (which really is 1); therefore, 71 = 71 * (7/7) = 497/7.

Now add them: (497 + 5)/7 = 502/7

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