The ratio of speed of a motor-boat to that of the current of water is 17 : 5. The boat goes along with the current in 4 hours. It will come back in-

Question: The ratio of speed of a motor-boat to that of the current of water is 17 : 5. The boat goes along with the current in 4 hours. It will come back in-

Solution:
Since the ratio 17 : 5 is given.
Let the speed of boat in still water = 17 km/hr
and speed of stream = 5 km/hr

Downstream speed = 17 + 5 = 22 km/hr
Upstream speed = 17 - 5 = 12 km/hr

Distance = Downstream speed × downstream time
= 22 × 4 = 88 km

Upstream time = Distance/upstream speed
= 88/12
∴ Come back time = 7 hour 20 minute