The speed of a boat in still water is 30 mph. It takes the same time for the boat to travel 5 miles upstream as it does to travel 10 miles downstream. Find the speed of current

Answer 1

current speed is 10 mph

d=rt

distance = rate of speed times time traveled

t=d(downstream)/(r+c) = d(upstream)/(r-c), r=30 mph, c = speed of the current

5/(r-c) = 10/(r+c) = t = same for either trip

5/(30-c) = 10/(30+c)

1/(30-c) = 2/(30+c)

2(30-c) = 30+c

60-2c = 30+c

3c = 30

c = 10 mph

r+c= 40 mph

r-c= 20 mph

5 miles = 20 x t, t = 5/20 = 1/4 = 15 minutes

10 miles = 40 x t, t = 10/40 = 1/4 = 15 minutes