SOLUTION: if you are rowing a boat at 40 miles for 4 hours down stream and then 40 miles per hour back up stream for 10 hours what is the current

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Question 286060: if you are rowing a boat at 40 miles for 4 hours down stream and then 40 miles per hour back up stream for 10 hours what is the current
Answer by checkley77(12844) About Me  (Show Source):
You can put this solution on YOUR website!
D=RT
40=(R+C)4
40=4R+4C MULTIPLY THIS EQUATION BY 5
40=(R-C)10
40=10R-10C MULTIPLY THIS EQUATION BY 2 & ADD
200=20R+20C
80=20R-20C
----------------
280=40R
40R=280
R=280/40
R=7 MPH IS THE SPEED OF THE BOAT IN STILL WATER.
40=(7+C)4
40=28+4C
4C=40-28
4C=12
C=12/4
C=3 MPH FOR THE CURRENT SPEED.
PROOF:
40=(10*7-10*3
40=70-30
40=40