4GMAT - Online GMAT Preparation

When Y is divided by 2, is the remainder 1?

1. (-1)^(Y+2) = -1
2. Y is prime

The only time 1. (-1)^(Y+2) = -1 will be true when Y+2 is odd and Y should be odd too. Y can be 1 and in that case remainder is not 1 hence statement 1 is not sufficient. Statement 2 mentions that Y is prime. If Y is 2 then answer is no but if Y is 3 then yes. Hence, statement alone is not sufficient either. But if taken together we know that Y cannot be 1 or 2 hence Y>2. Say Y is 3 or 5 the remainder is 1.

So 1&2 together is sufficient.