A boat traveled 36 km downstream in 2 h. return trip upstream=3 h. Find rate of current.
Time multiplied by speed equals distance, which is the same both ways. Boad speed
is s, speed of current is c.
Downstream:
2 hr * (s + c) km/hr = 36 km
(s + c) km/hr = 18 km/hr
Upstream:
3 hr * (s - c) km/hr = 36 km
(s - c) km/hr = 12 km/hr
Add the two equations:
s + c = 18 km/hr
s - c = 12 km/hr
2s = 30 km/hr
2s = 30 km/hr
s = 15 km/hr the boat's speed
Substitute into equation:
s + c = 18 km/hr
15 km/hr + c = 18 km/hr
c = 18 km/hr - 15 km/hr
c = 3 km/hr the speed of the current