A boatman goes 2 km against the current of the stream in 1 hour and goes 1 km along the current in 10 minutes. How long will it take to go 5 km in stationary water?
40 minutes
1 hour
1 hr 15 min
1 hr 30 min
Explanation:
| Rate downstream =$ \left(\dfrac{1}{10} \times 60\right) $km/hr = 6 km/hr. |
Rate upstream = 2 km/hr.
| Speed in still water =$ \dfrac{1}{2} $(6 + 2) km/hr = 4 km/hr. |
| $\therefore$ Required time =$ \left(\dfrac{5}{4} \right) $hrs = 1$ \dfrac{1}{4} $hrs = 1 hr 15 min. |