DS Numbers

[MBAsa]

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.


My answer is C. But its wrong. Help anyone.

[srcc25anu]

St1: Tens digit of n is a factor of units digitt
24, 36, 48, 66 from all these examples we see that if tens digit is a FACTOR of units digit, the number must be composite.
the only exception could be when tens digit is 1 as 1 is a factor of all numbers but we are given that n > 20
Hence SUFFICIENT

St2: tens digit = 2
if n = 23, PRIME but if n = 21, COMPOSITE
hence Insufficient

Ans A

[Brent@GMATPrepNow]

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.

Target question: Is n composite?

Given: n > 20

Statement 1: The tens digit of n is a factor of the units digit of n
It doesn't take long to list the 2-digit numbers that satisfy this condition:
22, 24, 26, 28
33, 36, 39
44, 48
55
66
77
88
99
All of these possible values of n are composite, so n must be composite.
Since we can answer the target question with certainty, statement 1 is SUFFICIENT

Statement 2: The tens digit of n is 2.
There are several values of n that meet this condition. Here are two:
Case a: n = 21, in which case n is composite
Case b: n = 23, in which case n is not composite
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Answer = A

Cheers,
Brent