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composite problem

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composite problem

by gmat009 » Tue Oct 07, 2008 12:25 pm
An integer greater than 1 that is not prime is called composite. If the two-digit integer n is greater than 20, is n composite?
(1)The tens digit of n is a factor of the units digit of n.
(2)The tens digit of n is 2.

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.

OA is A

IMO C
In option A I am getting 26(non-prime number) & 13(prime number). So according to me A is not sufficient. I am not sure why my answer is not correct.
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by namitrajiv » Tue Oct 07, 2008 12:31 pm
It has been mentioned in the statement that n >20

the values we can have using option 1 are

22, 24, 26, 28, 33, 36, 39, 44, 48, 55, 66, 77, 88, 99
all composite , thus A is the ans
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by gmat009 » Tue Oct 07, 2008 12:34 pm
namitrajiv wrote:It has been mentioned in the statement that n >20

the values we can have using option 1 are

22, 24, 26, 28, 33, 36, 39, 44, 48, 55, 66, 77, 88, 99
all composite , thus A is the ans
Sorry I missed that point.
Thanks....
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by cubicle_bound_misfit » Tue Oct 07, 2008 12:58 pm
instead of finding composite no try to find all the prime no < 99 > 20

the list will show n shud be a composite no. if it satisfies stmt 1.

there can be nos not satisfying stmt 1 yet not prime like 25 but at least it will not be prime.
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by farooq » Wed Jan 20, 2010 9:42 am
gmat009 wrote:An integer greater than 1 that is not prime is called composite. If the two-digit integer n is greater than 20, is n composite?
(1)The tens digit of n is a factor of the units digit of n.
(2)The tens digit of n is 2.

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.

OA is A

IMO C
In option A I am getting 26(non-prime number) & 13(prime number). So according to me A is not sufficient. I am not sure why my answer is not correct.
Two digit number can be TU
T = Tenth Digit.
U= Unit Digit.

T is a factor of U.

if T is a factor of U means number is always divisible by T.

24...divisible by 2
36....divisible by 3

Therefore the number is Non prime number. A is sufficient.

B: T=2, U = can be 1,2,3,...9 (29 is a prime number: NO, 22 is not a prime no: Yes)...Yes, No...Insufficient.
Regards,
Farooq Farooqui.
London. UK

It is your Attitude, not your Aptitude, that determines your Altitude.
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