a canal has a current

Question

a canal has a current of 2 mph. find the speed of Vanessa's remote-controlled boat in still water if it would go 11 miles downstream in the same time that it goes 8 miles upstream.

Answer 1

distance = speed * time

let speed pf boat in still water = u

speed of current = 2

 

Upstream, speed reduced, therefore net speed = u-2

8= (u-2)*t

t= 8/(u-2)

 

Downstream, speed increased, therefore net speed = u+2

11=(u+2)*t

t=11/(u+2)

 

As both the upstream journey and downstream journey take same time

 

11/(u+2) =8/(u-2)

11u-22=8u+16

3u=38===> u =38/3 mph