gmat prep question

[yvonne12]

if c and d are integers, is C even?

1. c(d+1) is even

2. (c+d)(d+4) is even

[Prasanna]

Is the answer E?

Both the statements does not tell us whether c would be even or odd. Even taking them together I do not see a way to determine it.

[Princeton Review]

Plug in numbers here.

For statement 1, let's say that c=2 and d=2. These are acceptable numbers, since the make c(d+1)=2(2+1)=6, which is even. And for these numbers, c is even.

But you could also have c=1 and d=1, since 1(1+1)=2, which is even, so those values satisfy the statement. (When you're plugging in on Yes/No data sufficiency, the most important thing is to satisfy the statement.) And here, c is not even, so the statement is insufficient.

Similar deal for statment 2--in fact, you can use the same values. So 2 is insufficient.

And when we look at them together, again, both sets of values work in both statements, so together they're insufficient. So the answer is E.

[yvonne12]

thats exactly what I thought, but apparently its c

[bww]

yvonne12, can you post the explanation (if available)? i think the answer is "E" as well.

thanks.

[dunkin77]

Is OA C??

to produce odd result, both numbers have to be odd....but from 1) (d+1) and from 2) (d+4), it is impossible to produce odd using the same d...


Can anyone please explain?