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# Am I an idiot? If x is a positive number and 1/2 times the

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Senior Manager
Joined: 13 Jun 2007
Posts: 410
Schools: Wharton, Booth, Stern
Am I an idiot? If x is a positive number and 1/2 times the [#permalink]

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23 Jul 2007, 13:27
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

Am I an idiot?

If x is a positive number and 1/2 times the square root of x equals 2x, what is the value of x?

0
1/16
1/4
1/2
1

I got 1/4, and the answer is 1/16. Ok, it's late, but still, i can't be that bad??
Senior Manager
Joined: 17 Jul 2007
Posts: 288
Location: The 408

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23 Jul 2007, 13:42
I got B 1/16

I eliminated 1 and 0 (zero, I think would be undefined, 1 would be itself)

I plugged in answers (fast for me), so no help on a formula.
Manager
Joined: 22 May 2007
Posts: 121

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23 Jul 2007, 13:45
Agree. Just plug in and you get 1/16. Don't see where the problem is.
Intern
Joined: 14 Feb 2007
Posts: 24

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23 Jul 2007, 13:47
Hey man that's funny...I can relate...
Senior Manager
Joined: 13 Jun 2007
Posts: 410
Schools: Wharton, Booth, Stern

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23 Jul 2007, 14:50
Sorry guys, just made a fool of myself, of course it was 1/16. I overcomplicated things by trying to resolve the equation, and made a very silly mistake.

Morality: better take the values and replace them in the initial equation...
Director
Joined: 30 Nov 2006
Posts: 591
Location: Kuwait

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23 Jul 2007, 15:22
sqrt(x)/2 = 2x --> sqrt(x) = 4x

Senior Manager
Joined: 28 Jun 2007
Posts: 454

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23 Jul 2007, 16:45
sqrt(1/16) = 1/4 * 1/2 = 1/8 = 2*1/16

But common... How can you forget to PLUG IN at nights???

Just kidding
GMAT Club Legend
Joined: 07 Jul 2004
Posts: 5043
Location: Singapore

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23 Jul 2007, 19:20
1/2sqrt(x) = 2x
sqrt(x) = 4x
x = 16x^2
x(16x-1) = 0
x = 0, x = 1/16

Since question says x is positive, then x = 1/16
23 Jul 2007, 19:20
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