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divya23: Master | Next Rank: 500 Posts; Posts: 113; Joined: Mon Apr 26, 2010 8:58 amFollowed by: 14 members; Thanked: 2 times

by divya23 » Mon Jun 06, 2011 10:38 am

IF WX = Y
find xy ??
1. wx^2 = 16
2. y = 4

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Source: Beat The GMAT — Data Sufficiency | Mon Jun 06, 2011 10:38 am

Frankenstein: Legendary Member; Posts: 1448; Joined: Tue May 17, 2011 9:55 amFollowed by: 53 members; Location: India; Thanked: 375 times

by Frankenstein » Mon Jun 06, 2011 10:45 am

Hi,
wx=y
From(1):(wx).x=16 =>y.x = 16
Sufficient
From(2): y=4. we need to know to know the value of x or w to find xy.
Insufficient

Hence, A

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cans: Legendary Member; Posts: 1309; Joined: Mon Apr 04, 2011 5:34 amFollowed by: 123 members; Location: India; Thanked: 310 times; GMAT Score:750

by cans » Mon Jun 06, 2011 5:09 pm

wx=y
a)wx^2 = 16
wx*x=16
y*x=16
sufficient.
b)y=4
but we don't know value of x. insufficient.
IMO A

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GMATGuruNY: GMAT Instructor; Posts: 15539; Joined: Tue May 25, 2010 12:04 pmFollowed by: 1906 members; Location: New York, NY; Thanked: 13060 times; GMAT Score:790

by GMATGuruNY » Mon Jun 06, 2011 5:19 pm

divya23 wrote:IF WX = Y
find xy ??
1. wx^2 = 16
2. y = 4

An efficient approach -- one that doesn't require any algebraic insight -- would be to plug in two sets of values that satisfy the conditions given. If the value of xy stays the same, then the statement is sufficient. If the value of xy changes, then the statement is insufficient.

Statement 1: w(x^2) = 16
Let w=4, x=2, so that 4*(2^2) = 16.
Then y = wx = 4*2 = 8.
xy = 2*8 = 16.

Let w=16, x=1, so that 16*(1^2) = 16.
Then y = wx = 16*1 = 16.
xy = 1*16 = 16.

Since the value of xy stays the same, sufficient.

Statement 2: y=4
No way to determine the value of x.
Insufficient.

The correct answer is A.

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