GMAT prep question powers

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GMAT prep question powers

by mbadrew » Tue Aug 04, 2009 9:41 am
2^5 + 2^5 + 3^5 + 3^5 + 3^5

a. 5^6
b. 13^5
c. 2^7 + 3^8
d. 4^5 + 9^5
e. 2^6 + 3^6

I know this question has to be solved by factoring, but not sure how to approach.

OA after a few explanations.

thanks
Andrew

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by Neo2000 » Tue Aug 04, 2009 10:23 am
This is of the form a+a + b+b+b = 2a + 3b

So now you have 2.2^5 + 3.3^5

But you know that 2.2 = 2^2 and 2.2^2 =2^3 i.e. a^m x a^n = a^(m+n)

So you get 2^6 + 3^6

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Re: GMAT prep question powers

by ankitns » Tue Aug 04, 2009 10:24 am
Answer is E.

2^5 + 2^5 + 3^5 + 3^5 + 3^5
= (2^5 + 2^5) + (3^5 + 3^5 + 3^5)
= 2^5(1 + 1) + 3^5(1 + 1 + 1)

= 2^5(2) + 3^5(3)
=2^6 + 3^6


Hope it helps.
mbadrew wrote:2^5 + 2^5 + 3^5 + 3^5 + 3^5

a. 5^6
b. 13^5
c. 2^7 + 3^8
d. 4^5 + 9^5
e. 2^6 + 3^6

I know this question has to be solved by factoring, but not sure how to approach.

OA after a few explanations.

thanks
Andrew
Attempt 1: 710, 92% (Q 42, 63%; V 44, 97%)
Attempt 2: Coming soon!

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by mbadrew » Tue Aug 04, 2009 12:49 pm
Yes, OA is e.

Many thanks to both of you for explaining. I did get to the last part but wasn't sure about the answer.

thanks
Andrew