Question

The mad river flows at a rate of 2 KM/H. In order for a boat to travel 79.2 KM of River and then return in a total of eight hours how fast must about travel in Still water?

Answer 1

time upriver=distance/(S-2)
time downriver= distance/(s+2)

8hours=79.2 ( 1/(s-2) + 1/(s+2))

a bit of algebra, but get a common denominator on the right (s^2-4),
8hours=79.2 ( s+2 + s-2)/s^2-4

then combine, put it in quadratic form, and solve for s.

Answer 2

You should be able to get 20 km/h as your answer.