GRE Math : Exponential Operations

Study concepts, example questions & explanations for GRE Math

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Example Questions

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 relationship cannot be determined from the information given.

The two quantities are equal.

Quantity B is greater.

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.

The quantities are equal.

Quantity A is greater.

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 #3 : How To Multiply Exponents

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

Possible Answers:

10x7y + 7y2

10x11 + 7y3

None of the other answers

10x7 + 7y

10x7 + 7y3

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 #4 : How To Multiply Exponents

Quantitative Comparison

 

Quantity A: x3/3

Quantity B: (x/3)3

Possible Answers:

The relationship cannot be determined from the information given.

Quantity B is greater.

The two quantities are equal.

Quantity A is greater.

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:

The relationship cannot be determined from the information given.

The two quantities are equal.

Quantity A is greater.

Quantity B is greater.

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 #8 : How To Multiply Exponents

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.

Example Question #1563 : Gre Quantitative Reasoning

Which of the following is equal to ?

Possible Answers:

Correct answer:

Explanation:

 is always equal to ; therefore, 5 raised to 4 times 5 raised to 5 must equal 5 raised to 9.

 

is always equal to . Therefore, 5 raised to 9, raised to 20 must equal 5 raised to 180.

Example Question #21 : Exponential Operations

Which of the following is equal to ?

Possible Answers:

Correct answer:

Explanation:

First, multiply inside the parentheses: .

Then raise to the 7th power: .

Example Question #22 : Exponential Operations

Simplify:

(6x^{2})^{3}\cdot x^{-7}\cdot 2x^{4}

Possible Answers:

12x^{2}

6x^{2}

Correct answer:

Explanation:

Remember, we add exponents when their bases are multiplied, and multiply exponents when one is raised to the power of another. Negative exponents flip to the denominator (presuming they originally appear in the numerator). 

(6x^{2})^{3}\cdot x^{-7}\cdot 2x^{4}

 

Example Question #23 : Exponential Operations

 is a real number such that .

Quantity A:

 

Quantity B:

Possible Answers:

Quantity B is greater.

The two quantities are equal.

Quantity A is greater.

The relationship cannot be determined from the information given.

Correct answer:

The relationship cannot be determined from the information given.

Explanation:

(y2)(y4) = y2+4 = y6

Plug in two different values for y.

Plug in y = 1: y8 = y

Plug in y = 2: y8 > y

Since the results differ, the relationship cannot be determined from the information given.

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