GRE Math : How to find a solution to a compound fraction

Study concepts, example questions & explanations for GRE Math

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Example Questions

Example Question #1 : Fractions

Edward rolls three dice; two are six-sided, and one is twenty-sided, with 1 through 6 represented on the six-sided dice, and 1 through 20 represented on the twenty-sided die.

What is the probability that the sum of his roll will equal 5?

Possible Answers:

Correct answer:

Explanation:

The first step will be to calculate how many total different potential rolls are possible. This is given by the product of the number of possible rolls for each of the dice: 6, 6, 20:

Next it is necessary to account for the total number of rolls that will sum up to 5. Writing them out can help, such as in the format of:

Knowing that there are 6 different rolls that sum up to 5, the probability of rolling a 5 can be found by taking the number of events that satisfy this sum and dividing it by the number of total possible events:

Example Question #1 : How To Find A Solution To A Compound Fraction

Simplify the following:

Possible Answers:

Correct answer:

Explanation:

Looking at this equation, note that since all terms in the numerator and denominator contain a , it is possible to rewrite it as follows:

or

Now the parenthetical terms must be addressed. The problem statement and answer choices give a clue that they are some sort of multiples of .

In fact, Pascal's triangle reveals that the top and bottom are the cube and square of this term respectively:

Cancelling terms, we are left with:

Example Question #2 : How To Find A Solution To A Compound Fraction

 is a repeating decimal. What digit is in the  place?

Possible Answers:

Correct answer:

Explanation:

Examination of the value  reveals that after the sequence , the decimal repeats, and that the sequence has a length of eight values.

A longer answer would be to write the sequence out and count down the digits until the  value was found. However, this is a time-consuming process and one that is prone to error.

Rather, notice how since the numbers repeat, it's possible to skip most of the counting:

 digit: 

 digit: 

And so on. Since  is the closest multiple to , we can subtract the two to find the digit that matches the  digit.

So the  digit is .

Example Question #4 : Fractions

Which of the following is equal to   of the reciprocal of  percent?

Possible Answers:

Correct answer:

Explanation:

The first step will be to find the reciprocal of  percent. Note that as a percent, this should be converted to a decimal form: .

The reciprocal of a number is given by  divided by that number, so the reciprocal of  is given as:

Therefore:

Example Question #3 : How To Find A Solution To A Compound Fraction

 percent of  is .

 percent of  is .

Quantity A: 

Quantity B: 

Possible Answers:

The two quantities are equal.

Quantity B is greater.

Quantity A is greater.

The relationship between A and B cannot be determined.

Correct answer:

The two quantities are equal.

Explanation:

To make the comparison, the values of  and  must be determined.

We are told that  percent of  is , so its value can be determined as follows:

With  known, it is possible to find , since  percent of  is :

The two quantities are equal.

Example Question #4 : How To Find A Solution To A Compound Fraction

 can be rewritten as  times what?

Possible Answers:

Correct answer:

Explanation:

To solve this problem, realize that a decimal may be placed at the very end of this integer:

Now, count how many spaces the decimal will need to move to the left to reach:

 

It must move a total of  spaces, so:

 

Example Question #7 : Fractions

Simplify: 

Possible Answers:

Correct answer:

Explanation:

To solve this problem, begin with simplifying the numerator. This can be done by first finding a common denominator. For

a common denominator would be :

or

Which combines into:

But recall that this is just the numerator, and there is still a  in the denominator:

So, the final answer is:

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