Question

A boat covers 12km upstream and 18km downstream in 3hrs. While it covers 36km up stream and 24km downstream in 6(1/2) hrs. Find velocity of the stream?



a.1.5kmph



b.1kmph



c.2kmph



d.2.5kmph.

Answer 1

Answer:

2 km/h

Explanation:

let the upstream velocity = u1 .

let the downstream velocity = u2

12/ u1 + 18/u2 = 3 hours

similarly

36/ u1 + 24/u2 = 13/2 hours

36/ u1 + 54/u2 = 9 = 18/2

30/u2 = 5/2 ,  u2 = 12

36/u1 = 9/2  , u1 = 8

Now let the boat velocity = b and the stream velocity = s

upstream u1 = b - s  = 8

down stream u2 =  b + s = 12

s = 2 km/h