You can put this solution on YOUR website! How do you find the current of a river when the paddle boat takes 57 min to travel 4 miles up and back at a speed 10miles per hour?
:
Let c = the rate of the current
then
(10-c) = effective speed up-river
and
(10+c) = effective speed down-river
:
Convert 57 min to hrs; 57/60
:
Write a time equation, time = dist/speed + =
multiply 60(10+c)(10-c)
60(10+c)(10-c)* + 60(10+c)(10-c)* = 60(10+c)(10-c)
cancel the denominators
60(10+c)*4 + 60(10-c)*4 = 57(10+c)(10-c)
2400 + 240c + 2400 - 240c = 57(100-c^2)
4800 = 5700 - 57c^2
57c^2 = 5700 - 4800
57c^2 = 900
c^2 =
c =
c = 3.97 ~ 4 mph is the current
:
:
Check this, find the actual time each way
4/6 = .667 hrs
4/14 = .285 hrs
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total: .952 hrs which is .952(60) = 57 min
