A river flows at 3km/h. At what speed must a boat travel in order to make a 35km trip upstream in a time of 50 minutes?

Question

How long will it take the boat to make the return trip downstream? (Assume the boat retains the speed travelled upstream)
Working out please

Answer 1

u = boat speed
u-3 = upstream speed
u+3 = downstream speed

distance = speed * time

35 = (u-3) * 5/6
210 = 5u - 15
225 = 5u
45 = u

downstream,

35 = 48 * t
t = 35/48
t = 0.729 hr = 43min 45 sec

Answer 2

BAD QUESTION