GRE Math : How to find a rational number from an exponent

Study concepts, example questions & explanations for GRE Math

varsity tutors app store varsity tutors android store varsity tutors ibooks store

Example Questions

Example Question #1 : How To Find A Rational Number From An Exponent

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

     43                              34 

Possible Answers:

The two quantities are equal.

The answer cannot be determined from the information given.

Quantity A is greater.

Quantity B is greater.

Correct answer:

Quantity B is greater.

Explanation:

In order to determine the relationship between the quantities, solve each quantity.

4is 4 * 4 * 4 = 64

34 is 3 * 3 * 3 * 3 = 81

Therefore, Quantity B is greater.

Example Question #2 : How To Find A Rational Number From An Exponent

Quantity A: \(\displaystyle (-1)^{137}\)

Quantity B: \(\displaystyle 0\)

Possible Answers:

The relationship cannot be determined from the information given. 

Quantity A is greater.

Quantity B is greater.

The two quantities are equal.

Correct answer:

Quantity B is greater.

Explanation:

(–1) 137= –1   

–1 < 0

(–1) odd # always equals –1.

(–1) even # always equals +1.

Example Question #33 : Algebra

\(\displaystyle 2^{-5}\)

 

Possible Answers:

\(\displaystyle 2\)

\(\displaystyle \frac{1}{32}\)

\(\displaystyle 32\)

\(\displaystyle -32\)

\(\displaystyle -\frac{1}{32}\)

Correct answer:

\(\displaystyle \frac{1}{32}\)

Explanation:

Anything raised to negative power means \(\displaystyle 1\) over the base raised to the postive exponent. 

\(\displaystyle 2^{-5}=\frac{1}{2^5}=\frac{1}{32}\)

Example Question #15 : Exponents And Rational Numbers

Which of the following is not the same as the others?

Possible Answers:

\(\displaystyle 16^8\)

\(\displaystyle 2^{24}\)

\(\displaystyle (\frac{1}{2})^{^{-24}}\)

\(\displaystyle 64^4\)

\(\displaystyle 4^{12}\)

Correct answer:

\(\displaystyle 16^8\)

Explanation:

Let's all convert the bases to \(\displaystyle 2\).

\(\displaystyle 4^{12}=[2^2]^{12}=2^{24}\)

\(\displaystyle 64^4=(2^6)^4=2^{24}\)

\(\displaystyle 16^8=[2^4]^8=2^{32}\)

\(\displaystyle \left(\frac{1}{2}\right)^{^{-24}}\) This one may be intimidating but \(\displaystyle 2=\frac{1}{2}^{-1}\).

Therefore, 

\(\displaystyle \left(\left[\frac{1}{2}\right]^{-24}\right)^{-1}=2^{24}\)

\(\displaystyle 2^{24}\)

\(\displaystyle 16^8\) is not like the answers so this is the correct answer.

Example Question #41 : Exponents

Simplify

\(\displaystyle 2^{10}+2^9\)

Possible Answers:

\(\displaystyle 2^{18}\cdot 3\)

\(\displaystyle 2^9\cdot 3\)

\(\displaystyle 2^{10}\)

\(\displaystyle 2^{19}\)

\(\displaystyle 2^{10}\cdot 3\)

Correct answer:

\(\displaystyle 2^9\cdot 3\)

Explanation:

Whenever you see lots of multiplication (e.g. exponents, which are notation for repetitive multiplication) separated by addition or subtraction, a common way to transform the expression is to factor out common terms on either side of the + or - sign. That allows you to create more multiplication, which is helpful in reducing fractions or in reducing the addition/subtraction to numbers you can quickly calculate by hand as you'll see here.

 

So let's factor a \(\displaystyle 2^9\).

We have \(\displaystyle 2^9(2+1)\).

And you'll see that the addition inside parentheses becomes quite manageable, leading to the final answer of \(\displaystyle 2^9\cdot 3\)

Tired of practice problems?

Try live online GRE prep today.

1-on-1 Tutoring
Live Online Class
1-on-1 + Class
Learning Tools by Varsity Tutors