How to multiply exponents

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GRE Quantitative Reasoning › How to multiply exponents

Questions 1 - 10
1

Quantity A:

(0.5)3(0.5)3

Quantity B:

(0.5)7

Quantity A is greater.

Quantity B is greater.

The two quantities are equal.

The relationship cannot be determined from the information given.

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

2

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

Quantity A is greater.

Quantity B is greater.

The quantities are equal.

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.

3

(b * b4 * b7)1/2/(b3 * bx) = b5

If b is not negative then x = ?

–2

–1

7

1

Explanation

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

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

4

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

1/5

2/5

√5

5/2

25

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.

5

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

10x7 + 7y3

10x11 + 7y3

None of the other answers

10x7 + 7y

10x7y + 7y2

Explanation

Let's do each of these separately:

x3 * 2x4 * 5y = 2 * 5 * x3 * x4 * 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

6

Quantitative Comparison

Quantity A: _x_3/3

Quantity B: (x/3)3

Quantity A is greater.

Quantity B is greater.

The two quantities are equal.

The relationship cannot be determined from the information given.

Explanation

First let's look at Quantity B:

(x/3)3 = _x_3/27. Now both columns have an _x_3 so 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.

7

Which of the following is equal to ?

Explanation

First, multiply inside the parentheses: .

Then raise to the 7th power: .

8

Simplify:

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

12x^{2}

6x^{2}

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}

9

Evaluate:

\dpi{100} \small 78

\dpi{100} \small 81

\dpi{100} \small 27

\dpi{100} \small 30

\dpi{100} \small 24

Explanation

Can be simplified to:

Capture2

10

Which of the following is equal to ?

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.

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