| A boatman goes 3 km against the current of the stream in 1 h and goes 1 km along the current in 15 min. How long will it take to go 7 km in stationary water? |
A) 2 h 15 min
B) 2 h
C) 2 h 30 min
D) 2 h 45 min
Correct Answer: B
Solution :
| Downstream speed \[=\left( \frac{1}{15}\times 60 \right)km/h=4\,\,km/h\] |
| Upstream speed \[=3\,\,km/h\] |
| Speed in still water \[=\frac{1}{2}(4+3)\,\,km/h=3.5\,\,km/h\] |
| \[\therefore \]Required time \[=\left( \frac{7}{3.5} \right)=2\,\,h\] |
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