A bicycle travels at a constant speed of $15 \mathrm{~km} / \mathrm{h}$. A bus starts $195 \mathrm{~km}$ behind the bicycle and catches up to the bicycle in 3 hours. What is the average speed of the bus in $\mathrm{km} / \mathrm{h}$ ?
(A) 65
(B) 80
(C) 70
(D) 60
(E) 50
Traveling at a constant speed of $15 \mathrm{~km} / \mathrm{h}$, in 3 hours the bicycle will travel $15 \times 3=45 \mathrm{~km}$.

At the start, the bicycle was $195 \mathrm{~km}$ ahead of the bus.

Therefore, in order to catch up to the bicycle, the bus must travel $195 \mathrm{~km}$ plus the additional $45 \mathrm{~km}$ that the bicycle travels, or $195+45=240 \mathrm{~km}$.

To do this in 3 hours, the bus must travel at an average speed of $240 \div 3=80 \mathrm{~km} / \mathrm{h}$.

ANSWER: (B)