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

u = boat speed
u3 = upstream speed
u+3 = downstream speed
distance = speed * time
35 = (u3) * 5/6
210 = 5u  15
225 = 5u
45 = u
downstream,
35 = 48 * t
t = 35/48
t = 0.729 hr = 43min 45 sec