If P is an odd integer and (P^2 + Q * R) is an even integer,

Hi All,

We're told that If P is an ODD integer and (P^2 + Q * R) is an EVEN integer. We're asked which of the following MUST be true. This question can be solved with a mix of Number Properties and TESTing VALUES.

To start, since P is ODD, we know that P^2 will also be ODD (since ODD^2 = ODD).
For (ODD + Q * R) to be EVEN, we know that (Q * R) must also be ODD. However we do NOT know whether Q and R are integers or not...

IF Q=1 and R=1, then all 3 variables are ODD.
IF Q=2 ad R = 1/2, then the 3 variables include one ODD, one EVEN and one non-integer.

Thus, none of the first 4 answers is always going to be true.

Final Answer: E

GMAT assassins aren't born, they're made,
Rich

BTGmoderatorDC wrote:If P is an odd integer and (P^2 + Q * R) is an even integer, then which of the following must be true?

A. either Q or R is an odd integer
B. either Q or R is an even integer
C. both Q and R are odd integer
D. both Q and R are even integers
E. nothing can be concluded

Since P is odd, P^2 is also odd.In order for P^2 + Q * R to be even, Q * R must be odd, since odd + odd = even. If we knew that both Q and R were integers, then necessarily both Q and R would have to be odd. However, Q could be 2 and R could be 1/2, in which case the product Q * R = 2 x 1/2 = 1 is still an odd integer. Therefore, we cannot conclude anything about the parity of Q and R. Thus, the answer is E.

Answer: E