Question

a man rows upstream in still water at 3 km/h and back to the same place at 5km/h; he takes 48 minutes altogether. how far upstream did he go ​

Answer 1

Step-by-step explanation:

Distance travelled upstream = 1.5 km

◆ Explanation -

Let s be the distance man go to. Also vm amd vr be velocity of man and that of riverstream respectively.

During upstream journey,

t1 = s / (vm-vr)

t1 = s / 3

During downstream journey,

t2 = s / (vm+vr)

t2 = s / 5

Total time taken is 48 min,

t = t1 + t2

0.8 = s/3 + s/5

0.8 = s × (3+5)/(5×3)

s = 1.5 km

Therefore, the man went 1.5 km upstream.