Roy kayaked up the river and then back in a total of 5 hours. The trip was 4 miles each way and the current was difficult. If Roy kayaked at a speed of 4 mph, what was the speed of the current? Round your answer to 2 decimal places.

Answer 1

let speed of current be x mph
Roy's speed with the current = 4+x
Roy's speed against the current = 4-x

time with the current = 4/(4+x)
time against current = 4/(4-x)
total time = 5

4/(4+x) + 4(4-x) = 5
multiply each term by (4+x)(4-x)
4(4-x) + 4(4+x) = 5(4-x)(4+x)
16 - 4x + 16 + 4x = 80 - 5x^2
5x^2 = 48
x^2 = 48/5
x = .....

Answer 2

4.3