A kayaker paddles upstream for 1.5 hours then turns his kayak around and returns to his tent in 1 hour. He travels 3 miles each way. What is the rate of the rivers current?

Answer 1

speed up = u -c
speed down = u+c

d = speed * time
3 = (u-c)1.5
3 = (u+c)1

1.5 u - 1.5 c = 3
1.5 u + 1.5 c = 4.5
--------------------- add
3 u = 7.5
u = 7.5/3

3 = 7.5/3 + c

c = (9-7.5)/3 = 2.5/3 = .83333333333333333333333333