Question

a boat took 5 hours to travel 60 km up a river, against the current. the return trip took 3 hours. find the speed of the boat in still water and the speed of the current.

if possible, show your steps

Answer 1

speed of boat in still water ---- x km/h
speed of current ---- y km/h

effective speed with the current = x+y km/h
effective speed against the current = x-y km/h

time to go 60 km against the current = 60/(x-y) hours = 5
5x - 5y = 60 or <b>x - y = 12</b>
time to go 60 km with the current = 60/(x+y) = 3
3x + 3y = 60 or <b>x + y = 20</b>

solve for x and y, (add the two equation to start)
time to go 60 km with the current = 60/(x-y) hours

60/(x+y) + 60/(x-y) =

Answer 2

Eq1: Vb - Vc = 60/5 = 12km/hr,
Eq2: Vb + Vc = 60/3 = 20 km/hr,
Add Eq1 and Eq2:
Vb - Vc = 12,
Vb + Vc = 20,
sum: 2Vb = 32,
Vb = 16 km/hr = Speed of the boat in still water,

Vb + Vc = 20,
16 + Vc = 20,
Vc = ?.