# Thread: Help with the means of exponents

1. ## Help with the means of exponents

I'm studying for the GRE and going through and reviewing. I have a question about the properties of the means of exponents, I hope this is the right place to post this thread. I'm doing a practice test and I came across this question that I can't figure out how they came to the answer:

If 1 + x + x2 + x3 = 60, then the average (arithmetic mean) of x, x2, x3, and x4 is equal to which of the following?
a) 12x
b) 15x
c) 20x
d) 30x
e) 60x

The correct answer is b) 15x but I can't figure out how to arrive at that answer.

Any input would be appreciated!

2. ## Re: Help with the means of exponents

Originally Posted by blync
I'm studying for the GRE and going through and reviewing. I have a question about the properties of the means of exponents, I hope this is the right place to post this thread. I'm doing a practice test and I came across this question that I can't figure out how they came to the answer:

If 1 + x + x2 + x3 = 60, then the average (arithmetic mean) of x, x2, x3, and x4 is equal to which of the following?
a) 12x
b) 15x
c) 20x
d) 30x
e) 60x

The correct answer is b) 15x but I can't figure out how to arrive at that answer.

Any input would be appreciated!
$AM = \frac{x+x^2+x^3+x^4}{4}=\frac{x(1+x+x^2+x^3)}{4}= \frac {60x}{4}=15x$

3. ## Re: Help with the means of exponents

Perfect! Thanks!