S = (2/n)/[1/x + 2/(3x)]
Numerator = 1/x + 2/(3x) = [3 + 2]/(3x) = 5/(3x)
Hence, S = (2/n)/[5/(3x)] = (6x)/(5n)
Statement 1: x = 2n
Hence, S = (6*2n)/(5n) = 12/5
Sufficient
Statement 2: n = 1/2
We don't know the value of x.
Not sufficient
The correct answer is A.
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Please help with fractions!
Source: Beat The GMAT — Problem Solving |
Anju Agarwal
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Backup Methods : General guide on plugging, estimation etc.
Wavy Curve Method : Solving complex inequalities in a matter of seconds.
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Quant Expert, Gurome
Backup Methods : General guide on plugging, estimation etc.
Wavy Curve Method : Solving complex inequalities in a matter of seconds.
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Statement 1: x=2nIf S = (2/n) / (1/x + 2/(3x)), what is the value of S?
1. x = 2n
2. n = 1/2
Try two cases.
Case 1: n=1 and x=2.
S = (2/1) / (1/2 + 2/(3*2)) = 2 / (1/2 + 1/3) = 2 / (5/6) = 12/5.
Case 2: n=2 and x=4.
S = (2/2) / (1/4 + 2/(3*4)) = 1 / (1/4 + 1/6) = 1 / (5/12) = 12/5.
Since S = 12/5 in each case, SUFFICIENT.
Statement 2: n = 1/2
No information about x.
INSUFFICIENT.
The correct answer is A.
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I believe this would be easiest to solve with simple substitution.
(1) You will notice you have a "N" in the numerator and after substitution, a N in the denominator. This will help you simply cancel the N's out and the answer will be independent of the variable N.... a numeric answer
SUFFICIENT
(2) After substitution, here, you are still left with X in the denominator and only the numerator can be solved. Since this will leave a variable in the answer, it is INSUFFICIENT.
Answer: A
(1) You will notice you have a "N" in the numerator and after substitution, a N in the denominator. This will help you simply cancel the N's out and the answer will be independent of the variable N.... a numeric answer
SUFFICIENT
(2) After substitution, here, you are still left with X in the denominator and only the numerator can be solved. Since this will leave a variable in the answer, it is INSUFFICIENT.
Answer: A
