GRE Math : Arithmetic

Study concepts, example questions & explanations for GRE Math

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Example Questions

Example Question #451 : Arithmetic

Choose the answer below which best expresses the following decimal as a fraction (choose the answer which has been reduced/simplified the most):

Possible Answers:

Correct answer:

Explanation:

To convert from a decimal to a fraction, simply put the digits over one followed by a number of zeroes equal to the number of digits:

You cannot reduce, as one of the numbers in the fraction is prime, so that's your final answer. 

Example Question #1035 : Gre Quantitative Reasoning

Choose the answer below which best expresses the following decimal as a fraction (choose the answer which has been reduced/simplified the most):

Possible Answers:

Correct answer:

Explanation:

To convert from a decimal to a fraction, simply put the digits over one followed by a number of zeroes equal to the number of digits:

Then, you can reduce for your final answer:

Example Question #1 : Operations

What is the result of adding  of  to ?

Possible Answers:

Correct answer:

Explanation:

Let us first get our value for the percentage of the first fraction. 20% of 2/7 is found by multiplying 2/7 by 2/10 (or, simplified, 1/5): (2/7) * (1/5) = (2/35)

Our addition is therefore (2/35) + (1/4). There are no common factors, so the least common denominator will be 35 * 4 or 140. Multiply the numerator and denominator of 2/35 by 4/4 and the numerator of 1/4 by 35/35.

This yields:

(8/140) + (35/140)  = 43/140, which cannot be reduced.

Example Question #2 : Operations

Reduce to simplest form:  

Possible Answers:

\frac{3}{8}

\frac{3}{4}

\frac{1}{4}

\frac{1}{3}

\frac{1}{12}

Correct answer:

\frac{1}{12}

Explanation:

Simplify expressions inside parentheses first: \dpi{100} \small \left (\frac{4}{3} \times \frac{3}{8} \right ) = \frac{12}{24} = \frac{1}{2}  and \dpi{100} \small \left (\frac{1}{4} \div \frac{3}{8} \right ) = \left (\frac{1}{4} \times \frac{8}{3} \right ) = \frac{8}{12} = \frac{2}{3}

 

Now we have: \frac{1}{4} + \frac{1}{2} - \frac{2}{3}

Add them by finding the common denominator (LCM of 4, 2, and 3 = 12) and then multiplying the top and bottom of each fraction by whichever factors are missing from this common denominator:

\dpi{100} \small \frac{1\times 3}{4\times 3} + \frac{1\times 6}{2\times 6} - \frac{2\times 4}{3\times 4} =\frac{3}{12} + \frac{6}{12} - \frac{8}{12} = \frac{1}{12}

Example Question #31 : Fractions

Quantity A: 

Quantity B: 

Which of the following is true?

Possible Answers:

The relationship between the two quantities cannot be determined.

The two quantities are equal.

Quantity B is larger.

Quantity A is larger.

Correct answer:

The two quantities are equal.

Explanation:

Start by looking at Quantity A. The common denominator for this expression is . To calculate this, you perform the following multiplications:

This is the same as:

, or 

This is the same as Quantity B. They are equal!

Example Question #453 : Arithmetic

Solve for :

Possible Answers:

Correct answer:

Explanation:

Begin by isolating the  factors:

Now, the common denominator of these two fractions is .  Therefore, multiply  by :

Now, you can subtract the left values:

Now, multiply both sides by :

Example Question #454 : Arithmetic

Simplify:

Possible Answers:

Correct answer:

Explanation:

Just like adding fractions, when you subtract fractions, you need to find a common denominator. For  and , the least common denominator is . In order to do your subtraction, you need to multiply appropriately to give your fractions this denominator:

Which is the same as...

Now, you can subtract the numerators and retain the denominator:

Example Question #1 : How To Subtract Fractions

Which of the following is true?

Quantity A: 

Quantity B: 

Possible Answers:

The relationship between the quantities cannot be determined.

Quantity A is larger.

Quantity B is larger.

The two quantities are equal.

Correct answer:

Quantity A is larger.

Explanation:

First, consider each quantity separately.

 

Quantity A

 

These two fractions do not have a common factor. Their common denominator is . Thus, we multiply the fractions as follows to give them a common denominator:

This is the same as:

 

Quantity B

 

The common denominator of these two values is .  Therefore, you multiply the fractions as follows to give them a common denominator:

This is the same as:

Since Quantity A is larger than  and Quantity B is a positive fraction less than , we know that Quantity A is larger without even using a calculator.

Example Question #1 : How To Multiply Fractions

There are 340 students at Saint Louis High School in the graduating senior class. Of these students, 9/10 are going to college.  Of those going to college, 2/5 are going to Saint Louis University. How many students are going to Saint Louis University?

Possible Answers:

122

The answer cannot be determined from the given information.

136

103

306

Correct answer:

122

Explanation:

122 students are going to Saint Louis University. To answer this question, the following equation can be used: 340*(9/10)*(2/5) .  This is then rounded down to 122 students attending Saint Louis University. 

Example Question #3 : Operations

If  of a number is , what is  of that number?

Possible Answers:

Correct answer:

Explanation:

The least common multiple of 4 and 6 is 12.

So we know if  of the number is  then 

 of the number is 

.

So then it follows that

of the number is 

.

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