Question

A boat covers 32 km upstream and 36 km downstream in 7 hours also,it cover 40 km upstream and 48 km downstream in 9h . Find the speed of the boat in still water and speed of stream

Answer 1

Let speed of boat in still water is x

Let speed of steam y

Thus speed of boat upstream is (x-y) km /hr

And downstream is x+y

Time taken to cover 32 km upstream is 32/x-y

Time taken to cover 36km downstream is36/x+y

According to question

32/x-y + 36/x+ y = 7 hrs

And 40/x-y + 48 / x+y = 9 hrs

Let 1/x-y=u and 1/x +y=v

Therefore 32u+36v=7............eq1

40u+49v=9..............eq2

Multiply eq1 by 5 and eq2 by 4 we get

160u+180v=35...........eq3

160u+192v=36.............eq4

On equating both we get

V=1/12 and u=1/8

Thus x-y=8 and x+y =12

On equating

X= 10 km/hr

Y=2km/hr