Q168
ArithmeticSpeed, Time & Distance
A man rows down a river 15 km is 3 hrs. with the stream and returns in $7\frac{1}{2}$ hrs. The rate at which he rows in still water is
- a.2·5 km/hr
- b.1·5 km/hr
- c.3·5 km/hr
- d.4·5 km/hr
Answer: (C) 3·5 km/hr
Downstream speed = 15 ÷ 3 = 5 km/hr and upstream speed = 15 ÷ 7·5 = 2 km/hr. Speed in still water = (5 + 2) ÷ 2 = 3·5 km/hr. 1·5 km/hr is the speed of the stream.