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Source: — Problem Solving |
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by pepeprepa » Sun Jul 20, 2008 9:24 am
You should write parenthesis, it could be confusing.

2^12 - 2^6 = (2^6)^2 - (2^3)^2 = (2^6+2^3)(2^6-2^3)
You put it in your numerator and delete both 2^6-2^3

So it is 2^6+2^3
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by mbaapplicant2008 » Fri Oct 31, 2008 12:07 am
Yes, the answer is B
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by cramya » Fri Oct 31, 2008 5:03 am
I think this problem has been solved in the forum.


2^12 - 2 ^ 6 = (2^6+2^3) (2^6-2^3) [
a ^ 2 - b ^ 2 = (a+b) (a-b)]

2^6-2^3 cancels out in the NUMERATOR AND DENOMINATOR leaving

2^6+2^3 as the answer

Hope this helps!
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by divs » Mon Nov 03, 2008 7:38 am
:!: ...still a beginner.... But can someone tell me why it cant be solved this way ?!

2^6 ( 2^2 -1 ) / 2^3 ( 2^2 -1 )

= 2^6 / 2^3

= 2^3 :!:
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by jnellaz » Mon Nov 03, 2008 10:51 am
I got the same answer as divs. Can any explain why this is wrong?
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by amitabhprasad » Mon Nov 03, 2008 11:13 am
I think you guys are trying to multiple exponents with same base. While exponents are added/subtracted with same base not multipled
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Explaining

by Hope700 » Mon Nov 03, 2008 11:19 am
divs wrote::!: ...still a beginner.... But can someone tell me why it cant be solved this way ?!

2^6 ( 2^2 -1 ) / 2^3 ( 2^2 -1 )

= 2^6 / 2^3

= 2^3 :!:
(2^6 ) (2^2) is not the same as 2^12

Remember that when you multiply integers with exponents , the exponents add together , they do NOT multiply themselves
Therefore

(2^6)(2^2) = 2^8 is not the same as

(2^6)(2^6) = 2^12 Be careful this GMAT Creators know about this easy mistakes
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by jnellaz » Mon Nov 03, 2008 1:43 pm
Thanks Hope700!
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by divs » Mon Nov 03, 2008 8:18 pm
sheeezz !!! Thanks Hope700.... !! that was a stupid goof up.... :roll:
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by vishubn » Tue Nov 04, 2008 5:39 am
Ya straight forward :) But again !! u never know the trap ! or the mistake we make :)

Vishu
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by Hope700 » Tue Nov 04, 2008 8:39 am
Well it happens sometimes

Have a good day all
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