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silver870
Is positive integer N divisible by 3?

(1) N^2/36 is an integer

(2) 144/N^2 is an integer

From (1) \(n^2/36\)= INT
Therefore the values for \(n^2\) that fit the condition = 36, 144 and so on
n= 6, 12 (bcoz \(n\) is positive int) and so on. Fact (1) SUFF
From (2) \(144/n^2\)= INT
Therefore \(n^2\) could be 1, 4, 9....
and when n= 1 (No), 2 (No), 3 (Yes). Fact 2 INSUFF
Hence A :-D
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A very useful property -> X and X^n always have the exact same prime factors.
For N to be divisible by 3 => 3 must be the prime factors of N.

Statement 1=>
N^2/36 is an integer.
N^2 has both 2 and 3 as it prime.
Thus N must have 3 as its prime too.
Hence Sufficient.
Statement 2=>
Lets use test Cases here.
N=1 => 144/1^2 =Integer => 1 is not divisible by 3.
N=3 => 144/N^2 =integer => 3 is divisible by 3.
Hence not sufficient.

Hence A
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I did this problem with difference approach. Can some one please evaluate is my approach towards this problem correct?
Attachments

problem.jpg
problem.jpg [ 1.41 MiB | Viewed 12672 times ]

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St 1: N sq/36 = integer. 36 is a multiple 3, so dvble by 3
St 2: 144/ N sq = integer. N = what? Not suff

Ans: A
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Hello from the GMAT Club BumpBot!

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