A man can row 9km/h in still water. If the river is running at 4km/h, it takes 8 hours more in upstream than to go downstream for the same distance. How far is the place?
- A65km
- B60km
- C75km
- D55km
Solution & Step-by-step Explanation
Given:
Speed of the man in still water (u) = 9km/h
Speed of the stream (v) = 4km/h
Downstream speed (D) = u+v=9+4=13km/h
Upstream speed (U) = u−v=9−4=5km/h
Let the distance to the place be dkm.
According to the problem, the difference in time taken is 8 hours:
Time
upstream
−Time
downstream
=8
5
d
−
13
d
=8
Taking the LCM of 5 and 13, which is 65:
65
13d−5d
=8
65
8d
=8
8d=8×65
d=65km
Therefore, the distance to the place is 65km.
Speed of the man in still water (u) = 9km/h
Speed of the stream (v) = 4km/h
Downstream speed (D) = u+v=9+4=13km/h
Upstream speed (U) = u−v=9−4=5km/h
Let the distance to the place be dkm.
According to the problem, the difference in time taken is 8 hours:
Time
upstream
−Time
downstream
=8
5
d
−
13
d
=8
Taking the LCM of 5 and 13, which is 65:
65
13d−5d
=8
65
8d
=8
8d=8×65
d=65km
Therefore, the distance to the place is 65km.