Question

A boat takes 8 hours to go 6 miles upstream and come back to the starting point. If the speed of the boat is 4 miles per hour in still water, what is the rate of the current? Hint: total time taken = time taken to go upstream + time taken to go downstream

Answer 1

Let x = velocity of the water current t1 = time taken to go downstream t2 = time taken to go upstream t1 + t2 = 8 t2 = 8 – t1 v = D/t Downstream (4 + x) = 6/ t1 t1 = 6/(4+x) Upstream (4 – x) = 6/t2 Substitute expression for t2 to obtain (4 – x) = 6/ (8-t1) Substituting the expression of t1 to make a single variable equation, obtaining 6 = (4-x)*(8 – 6/(4+x)) Solving for x, x= 3.16 m/s