Pot A has 15 glasses of water. Pot B holds thrice as much water as pot A. How many glasses of water are needed to fill Pot B.

Question

$\begin{array}{11} (a)\;\text{7 glasses of water} \\ (b)\; \text{9 glasses of water} \\ (c)\; \text{15 glasses of water} \\ (d)\; \text{45 glasses of water} \end{array}$