If $\frac{1}{3} x=12$, then $\frac{1}{4} x$ equals
(A) 1
(B) 16
(C) 9
(D) 144
(E) 64
Solution 1

Since $\frac{1}{3} x=12$, then $x=3 \times 12=36$, so $\frac{1}{4} x=\frac{1}{4}(36)=9$.

Solution 2

Since $\frac{3}{4} \times \frac{1}{3}=\frac{1}{4}$, then $\frac{1}{4} x=\frac{3}{4} \times\left(\frac{1}{3} x\right)=\frac{3}{4}(12)=9$.

ANSWER: (C)