GRE Math : Fractions

Study concepts, example questions & explanations for GRE Math

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Example Questions

Example Question #461 : Arithmetic

Car A traveled 120 miles with 5 gallons of fuel.

Car B can travel 25 miles per gallon of fuel.

Quantity A: The fuel efficiency of car A

Quantity B: The fuel efficiency of car B

Possible Answers:

Quantity A is greater.

Quantity B is greater.

The relationship cannot be determined.

The two quantities are equal.

Correct answer:

Quantity B is greater.

Explanation:

Let's make the two quantities look the same. 

Quantity A: 120 miles / 5 gallons =  24 miles / gallon

Quantity B: 25 miles / gallon

Quantity B is greater.

Example Question #52 : Fractions

Quantity A:

The -value of the equation  when 

Quantity B:

 

Possible Answers:

The relationship cannot be determined from the information given.

Both quantities are equal

Quantity A is greater.

Quantity B is greater.

Correct answer:

Quantity A is greater.

Explanation:

In order to solve quantitative comparison problems, you must first deduce whether or not the problem is actually solvable. Since this consists of finding the solution to an -coordinate on a line where nothing too complicated occurs, it will be possible.  

Thus, your next step is to solve the problem.

Since  and , you can plug in the -value and solve for :

Plug in y:

Add 2 to both sides:

Divide by 3/4.  To divide, first take the reciprocal of 3/4 (aka, flip it) to get 4/3, then multiply that by 5/3:

Make the improper fraction a mixed number:

 Now that you have what x equals, you can compare it to Quantity B. 

Since  is bigger than 2, the answer is that Quantity A is greater

 

Example Question #53 : Fractions

What is equivalent to ?

Possible Answers:

Correct answer:

Explanation:

Remember that when you divide by a fraction, you multiply by the reciprocal of that fraction.  Therefore, this division really is:

At this point, it is merely a matter of simplification and finishing the multiplication:

Example Question #54 : Fractions

Which of the following is equivalent to ?

Possible Answers:

Correct answer:

Explanation:

To begin with, most students find it easy to remember that...

From this, you can apply the rule of division of fractions.  That is, multiply by the reciprocal:

Therefore,

Since nothing needs to be reduced, this is your answer.

Example Question #1 : How To Find The Reciprocal Of A Fraction

Carpenter A takes 45 hours to build a table. Carpenter B takes 30 hours. When they work together, how long will it take them to build a table?

Possible Answers:

Correct answer:

Explanation:

Write their respective rates as fractions:

Carpenter A: \dpi{100} \small \frac{1\ table}{45\ hours}

Carpenter B: \dpi{100} \small \frac{1\ table}{30\ hours}

Add them together to find their combined rate.  First find a common denominator.  The smallest multiple of both 45 and 30 is 90:

\dpi{100} \small \frac{2}{90}+\frac{3}{90}=\frac{5}{90}=\frac{1\ table}{18\ hours}

Therefore, they take 18 hours to build a table together.

Example Question #1 : How To Find The Reciprocal Of A Fraction

What is the sum of the reciprocal of , the reciprocal of , the reciprocal of , and ?

Possible Answers:

None of the other answers

Correct answer:

Explanation:

Begin by finding the reciprocal of , the reciprocal of , and the reciprocal of :

In order to add the four terms together, we will need to find a common denominator. Find the common denominator by multiplying the three different terms in the denominator (x, y, and z). Our common denominator will be . Put each term into terms of this common denominator:

Now, add each term together:

Look for the answer choice that matches this.

 

Example Question #1 : Reciprocals

Find the reciprocal of the following expression:

Possible Answers:

Correct answer:

Explanation:

To find the reciprocal of a rational expression--any rational expression--all you need to do is flip the numerator and the denominator.  

Therefore, the correct answer is:

 

You can check this by multiplying the two expressions together and ensuring that your answer is .

Example Question #4 : How To Find The Reciprocal Of A Fraction

Find the reciprocal of the following expression:

Possible Answers:

Correct answer:

Explanation:

To find the reciprocal of any fraction, you merely need to invert the numerator and denominator.  

In this case, first you have to convert the mixed number into a fraction:

Therefore, the answer is:

Example Question #51 : Fractions

What is the least common denominator of  and ?

Possible Answers:

Correct answer:

Explanation:

To find the least common denominator of two numbers, it is easiest first to factor them into prime factors:

Now, you need to compare each number and choose the case in which the prime factor has the highest power.  Therefore, since  and  are found only in , you will select those.  You can take "either" .  Finally, the  in  is the largest factor of .  Your LCD is found by multiplying all of these together:

Example Question #2 : How To Find The Lowest / Least Common Denominator

Simplify:

Possible Answers:

Correct answer:

Explanation:

To begin to solve this, you need to find the least common denominator of  and .  The easiest way to do this is to begin by factoring them into prime factors:

The LCD is found by selecting the largest power for each factor across the two values.  Therefore, you will take ,, and  from  and the  from the .  Your LCD is therefore:

.

Now, apply this to your fractions:

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