Question

A boat goes 16km upstream & 24km downstream in 6 hours. Also, it covers 12km upstream and 36km downstream in the same time. Find the speed of the boat in still water and that of the stream.

Answer 1

Let the speed of boat be 'x' && speed of stream be 'y'
Downstream speed = x+y
Upstream speed = x-y
Given,
16/x-y + 24/x+y = 6.....(i)
12/x-y + 36/x+y =6....(ii)
(i)* 3 && (ii)*4
(i)== 48/x-y + 72/x+y = 18......(iii)
(ii)== 48/x-y + 144/x+y = 24...(iv)
(iv)-(iii)== 144-72/x+y = 24-18
72/x+y = 6
12/x+y = 1
x+y = 12....(a)
(a) in (i)
16/x-y + 24/12 = 6
16/x-y = 6-2 =4
4/x-y = 1
x-y = 4....(b)
(a) + (b) = 2x = 16
x = 8...y=4
Hence speed of boat = 8 km/hr
Speed of stream = 4 km/hr
Hope it helps.

Answer 2

hope it will help you..............