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Exponents

by vinay1983 » Fri Aug 30, 2013 3:01 am
[(8^2)(3^4)(2^4)]/(96^2)

(A) 3
(B) 6
(c) 9
(D) 12
(E) 18

OA is C

I chose C. This is how I did it.Where was I wrong?

64*81*16/96*96 yields 9 or [(2^6+4)*(3^4)]/(2^5)^2 * (3^2) yields 9
Last edited by vinay1983 on Fri Aug 30, 2013 6:32 am, edited 1 time in total.
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by Brent@GMATPrepNow » Fri Aug 30, 2013 5:49 am
vinay1983 wrote:[(8^2)(3^4)(2^4)]/(96^2)

(A) 3
(B) 6
(c) 9
(D) 12
(E) 18
Add some color: [(8^2)(3^4)(2^4)]/(96^2)

First, let's rewrite (96^2) so that it has terms that are similar to those in the numerator.

(96^2) = [(8)(12)]^2
= [(8)(3)(4)]^2
= [(8)(3)(2^2)]^2
= (8^2)(3^2)(2^4)

So, [(8^2)(3^4)(2^4)]/(96^2)
= [(8^2)(3^4)(2^4)]/(8^2)(3^2)(2^4)
= 3^2
= [spoiler]9 = C[/spoiler]

Cheers,
Brent
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by vinay1983 » Fri Aug 30, 2013 6:13 am
Brent@GMATPrepNow wrote:
vinay1983 wrote:[(8^2)(3^4)(2^4)]/(96^2)

(A) 3
(B) 6
(c) 9
(D) 12
(E) 18
Add some color: [(8^2)(3^4)(2^4)]/(96^2)

First, let's rewrite (96^2) so that it has terms that are similar to those in the numerator.

(96^2) = [(8)(12)]^2
= [(8)(3)(4)]^2
= [(8)(3)(2^2)]^2
= (8^2)(3^2)(2^4)

So, [(8^2)(3^4)(2^4)]/(96^2)
= [(8^2)(3^4)(2^4)]/(8^2)(3^2)(2^4)
= 3^2
= [spoiler]9 = C[/spoiler]

Cheers,
Brent
Thanks Brent, will keep it in mind.

But the OA is A=3 not C=9!

What about it?
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by Brent@GMATPrepNow » Fri Aug 30, 2013 6:19 am
vinay1983 wrote: But the OA is A=3 not C=9!
What about it?
Unless, you've transcribed the question incorrectly, the answer here is 9.
If the OA says otherwise, I'd have to say that the OA is incorrect :-)

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by vinay1983 » Fri Aug 30, 2013 6:32 am
Brent@GMATPrepNow wrote:
vinay1983 wrote: But the OA is A=3 not C=9!
What about it?
Unless, you've transcribed the question incorrectly, the answer here is 9.
If the OA says otherwise, I'd have to say that the OA is incorrect :-)

Cheers,
Brent
Sorry Brent.My bad!Edited OA!
Tell me is my method appropriate for solving such questions?

Thanks!
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by Brent@GMATPrepNow » Fri Aug 30, 2013 7:09 am
vinay1983 wrote: Tell me is my method appropriate for solving such questions?
Yes, you're approach works perfectly.

You basically found the prime factorization of the numerator and denominator to get . . .
[(8^2)(3^4)(2^4)]/(96^2) = [(2^10)(3^4)]/[(2^10)(3^2)]
= 3^2

Cheers,
Brent
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