Question

The boat speed in still water is 30 miles per hour. A boat travels for 3 hours downstream and returns the same distance in 5 hours.find the speed of the stream

Answer 1

7.5 mph.

Explanation:

Speed downstream = d / 3 = 30 + x where d = the distance , x =speed of the stream.

Speed upstream = d / 5 = 30 - x.

30 + x = d/3

30 - x = d/5

Adding the 2 equations

60 = d/3 + d/5

8/15 d = 60

d = 60 * 15 / 8 = 112.5 miles.

Now calculate x , the speed of the stream:

112.5 / 3 = 30 + x

x = 112.5 / 3 - 30

= 7.5 mph.