Operation Problem

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monteleone82: Junior | Next Rank: 30 Posts; Posts: 10; Joined: Thu Sep 03, 2009 11:38 am

by monteleone82 » Fri Jul 09, 2010 7:34 am

Please help with this question from GMAT Prep.

If the operation @ is defined for all positive integers x and w by x @ w = 2^x/2^w, then (3 @ 1) @ 3 =

A. 2
B. 4
C. 8
D. 16
E. 32

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Source: Beat The GMAT — Problem Solving | Fri Jul 09, 2010 7:34 am

kmittal82: Master | Next Rank: 500 Posts; Posts: 324; Joined: Mon Jul 05, 2010 6:44 amFollowed by: 3 members; Location: London; Thanked: 70 times

by kmittal82 » Fri Jul 09, 2010 7:42 am

2^x/2^y = 2^(x-y)

You need to work the value in the () first:

(3@1) = 2^(3-1) = 2^2 = 4
4 @ 3 = 2^(4-3) = 2
Answer is A

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amising6: Master | Next Rank: 500 Posts; Posts: 294; Joined: Wed May 05, 2010 4:01 am; Location: india; Thanked: 57 times

by amising6 » Fri Jul 09, 2010 7:45 am

monteleone82 wrote:Please help with this question from GMAT Prep.

If the operation @ is defined for all positive integers x and w by x @ w = 2^x/2^w, then (3 @ 1) @ 3 =

A. 2
B. 4
C. 8
D. 16
E. 32

x @ w = 2^x/2^w = 2^(x-y)
(3 @ 1) @ 3= (2^(3-1)) @3
=2^2@3
=4@3
=2^(4-3)
=2

Ideation without execution is delusion

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