The speed of a boat in still water is 7 km/hr and the speed of the stream is 5 km/hr. A man rows to a place at a distance of 52.8 km and comes back to the starting point. Find the total time (in hours) taken by him.​

Correct option is D

Given:

Speed of the boat in still water = 7 km/hr

Speed of the stream = 5 km/hr

Distance to the place = 52.8 km

Formula Used:

Time = $$\frac{\text{Distance}}{\text{Speed}}$$ 

Solution:​

Speed downstream = 7 + 5 = 12 km/hr

Speed upstream = 7 - 5 = 2 km/hr

Time taken for the downstream journey = $$\frac{52.8}{12} = 4.4 \, \text{hours}$$​​

Time taken for the upstream journey = $$\frac{52.8}{2} = 26.4 \, \text{hours}$$​​

Total time = 4.4 + 26.4 = 30.8 hours