Number prob

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Number prob

by GMAT12 » Thu May 14, 2009 6:42 pm
A positive number x is multiplied by 2, and this product is then divided by 3. If the positive square root of the result of these two operations equals x,what is the value of x?

A)9/4
B)3/2
C)4/3
D)2/3
E)1/2

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by DanaJ » Thu May 14, 2009 9:28 pm
x is multiplied by 2 ---- 2x

this product is then divided by 3 ---- 2x/3

sqrt(2x/3) = x ---- raise everything to the second power to get:

2x/3 = x^2 ---- subtract the left side from the right side

x^2 - 2x/3 = 0

x(x - 2/3) = 0 ---- has two solutions: 0 and 3/2. You'll have to pick 2/3, since 0 is not positive.

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by abhinav85 » Mon May 18, 2009 1:44 pm
Let the digit be x

1.................digit is multiplied by 2,it becomes 2x.

2................2x is divided by 3,it becomes 2x/3.

3.................the square root of 2x/3 that 4x^2/9 is equal to x.

then when we solve this we x=9/4. thats option A.

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by Svedankae » Thu May 21, 2009 11:30 am
abhinav85 wrote:
3.................the square root of 2x/3 that 4x^2/9 is equal to x.
youre squaring it instead of taking the square root. thats why you end up with the wrong answer

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by cramya » Fri May 22, 2009 11:09 pm
DanaJ's approach would be the easiest. For this prob we can always reverse engineer(doesnt take much time) to verify the answer we have choosen is indeed right. Just a suggestion....

Regards,
CR