SOLUTION: a boat traveled 72 miles downstream and back. The trip downstream took 3 hours. The trip back took 18 hours. Find the speed of the boat in still water and the speed of the current.

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Question 676243: a boat traveled 72 miles downstream and back. The trip downstream took 3 hours. The trip back took 18 hours. Find the speed of the boat in still water and the speed of the current.
Answer by ankor@dixie-net.com(22740) (Show Source):
You can put this solution on YOUR website!
a boat traveled 72 miles downstream and back.
The trip downstream took 3 hours. The trip back took 18 hours.
Find the speed of the boat in still water and the speed of the current.
:
Let s = boat speed in still water
let c = speed of the current
Then
(s+c) = effective speed downstream
and
(s-c) = effective speed upstream
:
Write a distance equation for each way; dist = time * speed
:
3(s+c) = 72
18(s-c) = 72
Simplify both equations, divide the 1st by 3 and the 2nd by 18 and you have
s + c = 24
s - c = 4
------------- adding equations eliminates c, find s
2s = 28
s = 28/2
s = 14 mph, boat speed in still water
:
I'll let you find the speed of the current
Check your solution in the original equations