SOLUTION: The speed of a river current is 4 mph. If a boat travels 20 miles downstream in the same time that it takes to travel 10 miles​ upstream, find the speed of the boat in still
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Question 1071860: The speed of a river current is 4 mph. If a boat travels 20 miles downstream in the same time that it takes to travel 10 miles upstream, find the speed of the boat in still water.
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
current is 4 mph
speed of boat =x
downstream, speed is 4+x and time is 20/x+4, because time is distance over speed.
upstream, speed is 4-x and time is 10/x-4
The two times are equal
so 20/x+4=10/x-4
20x-80=10x+40
10x=120
x=12 mph
16 mph downstream and takes 1h15m to go 20 miles (1.25 hr)
8 mph upstream and takes 1h15m to go 10 miles.
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