The speed of a boat in still water is 25 kmph. If it can travel 10 km upstream in 1 hr, what time it would take to travel the same distance downstream?
22 minutes
30 minutes
40 minutes
15 minutes
Explanation:
Speed of boat in still water = 25 km/hr
Speed upstream $=\dfrac{10}{1}$ = 10 km/hr
Speed of the stream = (25-10) = 15 km/hr
Speed downstream = (25+15) = 40 km/hr
Time taken to travel 10 km downstream $=\dfrac{10}{40}\text{ hours} = \dfrac{10 \times 60}{40}$ = 15 minutes