The speed of a boat in still water is 8 kmph. If it can travel 1 km upstream in 1 hr, what time it would take to travel the same distance downstream?
1 minute
2 minutes
3 minutes
4 minutes
Explanation:
Speed of the boat in still water = 8 km/hr
Speed upstream $=\dfrac{1}{1}$ = 1 km/hr
Speed of the stream = 8-1 = 7 km/hr
Speed downstream = (8+7) = 15 km/hr
Time taken to travel 1 km downstream $=\dfrac{1}{15}\text{ hr = }\dfrac{1 \times 60}{15}\text{= 4 minutes}$