MATH PROBLEM WITH SPEED

Question

The boat was traveling 12 km downstream, and 11 km upstream. If it took totally 1 hour the boat to travel and given that the speed of the river is 2 km/h, what is the speed of the boat travelled downstream?

Answer 1

distance = speed times time, let t = t going downstream, 0<t<1,

1 = 12/(r+2) + 11(r-2)

r^2 - 4 = 12(r-2) + 11(r+2)

r^2 -23 -2 = 0

r = 23.09

r+2 = speed downstream = 25.1 km/hr