GRE Math : Algebra

Study concepts, example questions & explanations for GRE Math

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Example Questions

Example Question #1 : How To Subtract Exponents

Quantitative Comparison

Quantity A: 64 – 32

Quantity B: 52 – 42

Possible Answers:

The relationship cannot be determined from the information given.

Quantity A is greater.

The two quantities are equal.

Quantity B is greater.

Correct answer:

Quantity A is greater.

Explanation:

We can solve this without actually doing the math. Let's look at 64 vs 52. 64 is clearly bigger. Now let's look at 32 vs 42. 32 is clearly smaller. Then, bigger – smaller is greater than smaller – bigger, so Quantity A is bigger.

Example Question #1561 : Gre Quantitative Reasoning

, and  is odd.

Quantity A: 

Quantity B: 

 

Possible Answers:

The relationship cannot be determined from the information given.

The two quantities are equal.

Quantity A is greater.

Quantity B is greater.

Correct answer:

Quantity A is greater.

Explanation:

The first thing to note is the relationship between (–b) and (1 – b):

 (–b) < (1 – b) because (–b) + 1 = (1 – b).

Now when b > 1, (1 – b) < 0 and –b < 0. Therefore (–b) < (1 – b) < 0.

Raising a negative number to an odd power produces another negative number.

Thus (–b)a < (1 – b)a < 0.

Example Question #1561 : Gre Quantitative Reasoning

(b * b* b7)1/2/(b3 * bx) = b5  

If b is not negative then x = ?

Possible Answers:

–1

7

–2

1

Correct answer:

–2

Explanation:

Simplifying the equation gives b6/(b3+x) = b5.  

In order to satisfy this case, x must be equal to –2.

Example Question #21 : Exponential Operations

If〖7/8〗n= √(〖7/8〗5),then what is the value of n?

 

Possible Answers:

2/5

1/5

5/2

√5

25

Correct answer:

5/2

Explanation:

7/8 is being raised to the 5th power and to the 1/2 power at the same time. We multiply these to find n.

Example Question #1561 : Gre Quantitative Reasoning

Quantity A:

 (0.5)3(0.5)3

 

Quantity B: 

(0.5)7

Possible Answers:

Quantity A is greater.

The two quantities are equal.

Quantity B is greater.

The relationship cannot be determined from the information given.

Correct answer:

Quantity A is greater.

Explanation:

When we have two identical numbers, each raised to an exponent, and multiplied together, we add the exponents together:


xaxb = xa+b

This means that (0.5)3(0.5)3 = (0.5)3+3 = (0.5)6

Because 0.5 is between 0 and 1, we know that when it is multipled by itself, it decreases in value. Example: 0.5 * 0.5 = 0.25. 0.5 * 0.5 * 0.5 = 0.125. Etc.

Thus, (0.5)6 > (0.5)7

Example Question #1562 : Gre Quantitative Reasoning

For the quantities below, x<y and x and y are both integers.

Please elect the answer that describes the relationship between the two quantities below:

Quantity A

x5y3

 

Quantity B

x4y4

Possible Answers:

The relationship cannot be determined from the information provided.

Quantity A is greater.

The quantities are equal.

Quantity B is greater.

Correct answer:

The relationship cannot be determined from the information provided.

Explanation:

Answer: The relationship cannot be determined from the information provided.

Explanation: The best thing to do here is to notice that quantity A is composed of two complex terms with odd exponents. Odd powers result in negative results when their base is negative. Thus quantity A will be negative when either x or y (but not both) is negative. Otherwise, quantity A will be positive. Quantity B, however, has two even exponents, meaning that it will always be positive. Thus, sometimes Quantity A will be greater and sometimes Quantity B will be greater. Thus the answer is that the relationship cannot be determined.

Example Question #1563 : Gre Quantitative Reasoning

Simplify: (x3 * 2x4 * 5y + 4y2 + 3y2)/y

Possible Answers:

10x7 + 7y3

10x7y + 7y2

10x11 + 7y3

10x7 + 7y

None of the other answers

Correct answer:

10x7 + 7y

Explanation:

Let's do each of these separately:

x3 * 2x4 * 5y = 2 * 5 * x* x* y = 10 * x7 * y = 10x7y

4y2 + 3y2 = 7y2

Now, rewrite what we have so far:

(10x7y + 7y2)/y

There are several options for reducing this.  Remember that when we divide, we can "distribute" the denominator through to each member.  That means we can rewrite this as:

(10x7y)/y + (7y2)/y

Subtract the y exponents values in each term to get:

10x7 + 7y

Example Question #1564 : Gre Quantitative Reasoning

Quantitative Comparison

 

Quantity A: x3/3

Quantity B: (x/3)3

Possible Answers:

Quantity A is greater.

Quantity B is greater.

The relationship cannot be determined from the information given.

The two quantities are equal.

Correct answer:

The relationship cannot be determined from the information given.

Explanation:

First let's look at Quantity B:

(x/3)3 = x3/27. Now both columns have an xso we can cancel it from both terms. Therefore we're now comparing 1/3 in Quantity A to 1/27 in Quantity B.  1/3 is the larger fraction so Quantity A is greater.

However, if , then the two quantities would both equal 0.  Thus, since the two quantities can have different relationships based on the value of , we cannot determine the relationship from the information given.

Example Question #1562 : Gre Quantitative Reasoning

Quantitative Comparison: Compare Quantity A and Quantity B, using additional information centered above the two quantities if such information is given.

Quantity A          Quantity B

 

(23 )2                       (22 )3                  

 

Possible Answers:

Quantity A is greater.

The relationship cannot be determined from the information given.

Quantity B is greater.

The two quantities are equal.

Correct answer:

The two quantities are equal.

Explanation:

The two quantites are equal. To take the exponent of an exponent, the two exponents should be multiplied.

(2)or 23*2 = 64   

(2)or 22*3 = 64   

Both quantities equal 64, so the two quantities are equal.

Example Question #11 : Exponential Operations

Compare  and .

Possible Answers:

The answer cannot be determined from the information given.

Correct answer:

Explanation:

To compare these expressions more easily, we'll change the first expression to have  in front. We'll do this by factoring out 25 (that is, ) from 850, then using the fact that .

When we combine like terms, we can see that . The two terms are therefore both equal to the same value.

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