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Is 5 a factor of N?

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Is 5 a factor of N?

by valleeny » Sun Jan 10, 2010 7:22 pm
Is 5 a factor of N?

1) 25 is a factor of 5N
2) 5N is a perfect square

My ans is D. Both in itself are sufficient but the official answer says C.
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by papgust » Sun Jan 10, 2010 10:46 pm
Even i'm getting D.

1. 25 is a factor of 5N

25=5*5
If 25 is a factor of 5N, N must have atleast one 5. So, 5 is a factor of N.
Sufficient.

2. 5N is a perfect square.

5N to be a perfect square, N must have atleast one 5. So, 5 is a factor of N.
Sufficient.
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by linkinpark » Mon Jan 11, 2010 9:10 am
N is not mentioned to be integer so I think there is a trap around that

consider in first statement N = 5*root(10) so 5N = 25*root 10
from second if 5N = perfect square and has 25 as factor, will give N to be a multiple of 5.
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by linkinpark » Mon Jan 11, 2010 9:11 am
by the way forgot to mention in stmt 2 alone you can take N=36/5 so 5N is perfect square
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by mehravikas » Mon Jan 11, 2010 6:52 pm
I agree that statement 2 is not sufficient by itself but statement 1 is.
According to your explanation if N = 5 root (10) still 5 would be a factor of N

Statement 2 is insufficient because N could be 1/5 5 * 1/5 = 1 which is a perfect sqaure
linkinpark wrote:N is not mentioned to be integer so I think there is a trap around that

consider in first statement N = 5*root(10) so 5N = 25*root 10
from second if 5N = perfect square and has 25 as factor, will give N to be a multiple of 5.
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