Question

F rahul rows 15 km upstream in 3 hours and 21 km downstream in 3 hours, then the speed of the stream is

Answer 1

Find the speed upstream:

Distance = 15 km

Time = 3 hours

Speed = Distance ÷ Time

Speed = 15 ÷ 3 = 5 km/h

Find the speed downstream:

Distance = 21 km

Time = 3 hours

Speed = Distance ÷ Time

Speed = 21 ÷ 3 = 7 km/h

Define x and y:

Let the speed of the stream be x

Let the speed of the boat be y

Solve x and y:

y - x = 5 ----------- [ 1 ]

y + x = 7 ----------- [ 2 ]

[ 1 ] + [ 2 ] :

2y = 12

y = 6

Sub y into equation [ 2 ]:

6 + x = 7

x = 1

Answer: Speed of the stream is 1 km/h