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A paddle-boat can move at a speed of 6 km/h in still water. The boat is paddled
16 km downstream in a river in the same time
it takes to go 8 km upstream. What is the speed of the river? please show work
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Let "u" be the speed of the river.
Then the speed of the paddle-boat floating downstream is 6 +u km/h.
and the speed of the paddle-boat floating upstream is 6 -u km/h.
Time it spends for floating 16 km downstream is hours.
Time it spends for floating 8 km upstream is hours.
These times are equal, so you have an equation
= .
To solve it, multiply both sides by (6+u)*(6-u). You will get
16(6-u) = 8(6+u), or
96 - 16u = 48 + 8u, or
48 = 24u.
Hence, u=2.
Answer. the speed of the river is 2 km/h.
For more similar solved problems of this type see the lessons
- Wind and Current problems
- More problems on upstream and downstream round trips
- Selected problems from the archive on the boat floating Upstream and Downstream
in this site.
Also, you have this free of charge online textbook in ALGEBRA-I in this site
- ALGEBRA-I - YOUR ONLINE TEXTBOOK.