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by vinni.k » Tue Nov 01, 2011 1:03 pm
*source:- "MGMAT"

Please help in solving the following question.

Cost is expressed by the formula tb^4. If b is doubled, by what factor has the cost increased ?

(A) 2
(B) 6
(C) 8
(D) 16
(E) 1/2

Answer is D

Regards
Vinni
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by gmatblood » Tue Nov 01, 2011 1:07 pm
IMO: 16

Cost is expressed by the formula tb^4. If b is doubled, by what factor has the cost increased ?

(A) 2
(B) 6
(C) 8
(D) 16
(E) 1/2

sub:

original: t=1, b=2 : tb^4 = 16
modified: t=1, b=4(doubled) : tb^4 = 256

Modified/original = 16
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by shankar.ashwin » Tue Nov 01, 2011 8:34 pm
Cost = t * b^4

New Cost = t * (2b)^4 = t * 16 b ^4

New Cost = 16 Cost
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by vinni.k » Wed Nov 02, 2011 9:04 am
I tried with few more smart numbers. Got it.

Thanks shankar.ashwin and gmatblood.

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by vaibhavgupta » Wed Nov 02, 2011 1:10 pm
vinni.k wrote:*source:- "MGMAT"

Please help in solving the following question.

Cost is expressed by the formula tb^4. If b is doubled, by what factor has the cost increased ?

(A) 2
(B) 6
(C) 8
(D) 16
(E) 1/2

Answer is D

Regards
Vinni
tb^4 .. t(2b)^4= 2*2*2*2*tb^4= 16tb^4 ..

Hence D it is! :)
If OA is A, IMO B
If OA is B, IMO C
If OA is C, IMO D
If OA is D, IMO E
If OA is E, IMO A

FML!! :/
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