A motorboat travels 102miles in 3hours going upstream It travels 138 miles going downstream in the same amount of time. What is the rate of the boat in still water and what is the rate of the current?

Answer 1

distance = rate of speed times time

time= distance/speed

t = d/(r + or - c)

3 = 102/(r-c) = 138/(r+c) where r= rate of speed in still water and c= speed of the current

3r+3c = 138

3r-3c = 102 add them to get

6r = 240

r = 240/6 = 40 mph = speed in still water

r+c = 138/3 = 46

c = 46-40 = 6 mph = speed of the current

upstream speed is 46 mph

downstream speed is 34 mph