### A motor boat takes 2 hours to travel a distance of 9 km downstream and it takes 6 hours to travel the same distance against the current. The speed of the boat in still water and that of the current (in km/h) respectively are:

A. 6, 5 km/h B. 3, 1.5 km/h C. 8, 5 km/h D. 9, 3 km/h Answer: Option B
Downstream speed, $=\frac{9}{2}=4.5 \mathrm{kmph}$ Upstream speed, $=\frac{9}{6}=1.5 \mathrm{kmph}$ Thus, speed of boat in still water, $=\frac{4.5+1.5}{2}=3 \mathrm{~km} / \mathrm{h}$ Speed of current, $=\frac{4.5-1.5}{2}=1.5 \mathrm{~km} / \mathrm{h}$