AHSME 1968 Problem 7

Let $O$ be the intersection point of medians $AP$ and $CQ$ of triangle $ABC.$ if $OQ$ is 3 inches, then $OP$, in inches, is: $\text{(A) } 3 \text{(B) } \frac{9}{2} \text{(C) } 6 \text{(D) } 9 \text{(E) } \text{undetermined}$