A steamer can row at the speed of 16 km/hr in still water. If the river is flowing at 8 km/hr and it takes 12 hours for a round trip, then the distance between the two places is:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 72 km
Let the distance be d km. The downstream and upstream speeds are
Downstream: 16 + 8 = 24 km/hr
Upstream: 16 − 8 = 8 km/hr
The round trip takes 12 hours:
\( \displaystyle \frac{d}{24} + \frac{d}{8} = 12 \)
\( \displaystyle \frac{d + 3d}{24} = 12 \)
\( \displaystyle \frac{d}{6} = 12,\quad d = 72 \)
So the distance is 72 km (3 hours downstream and 9 hours upstream).