Question 732118
let current speed = x

boat speed =2 mph

against current 2-x
with current x+2

2/(x+2)+2/(2-x) = 5

2(2-x)+2(x+2)=5(4-x^2)

4-2x+2x+4 = 20-5x^2

5x^2=12
x^2= 12/5

x= sqrt(12/5)

upstream speed = 2- 1.55= 0.45 mph
downstream speed = 2+sqrt(12/5)= 3.55 mph

downstream time = 2/3.55= 0.56 hours
upstream time = 2/0.45=4.44 
Total time = 5 hours