SOLUTION: A boy swims downstream 0.9 miles in the same amount of time that he can swim 0.6 miles upstream. If the rate of the current is 1.5 mph, how fast can he swim in still water?

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Question 280396: A boy swims downstream 0.9 miles in the same amount of time that he can swim 0.6 miles upstream. If the rate of the current is 1.5 mph, how fast can he swim in still water?
Found 2 solutions by checkley77, richwmiller:
Answer by checkley77(12844) About Me  (Show Source):
You can put this solution on YOUR website!
D=RT
.9=(R+1.5)T SWIMMING DOWNSTREAM.
T=.9/(R+1.5)
.6=(R-1.5)T SWIMMING UPSTREAM.
T=.6/(R-1.5)
THE TIMES ARE THE SAME THUS SET THE TWO EQUATIONS EQUAL.
.9/(R+1.5)=.6/(R-1.5) CROSS MULTIPLY.
.9(R-1.5)=.6(R+1.5)
.9R-1.35=.6R=+.9
.9R-.6R=.9+1.35
.3R=2.25
R=2.25/.3
R=7.5 MPH IS THE SPEED OF THE SWIMMER IN STILL WATER.
PROOF:
.9/(7.5+1.5)=.6(7.5-1.5)
.9/9=.6/6
.1=.1

Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
rt=d
(r+1.5)*t=.9 miles
(r-1.5)*t=.6 miles
r=7.5 mph in still water
t=.1
check
9t=.9
6t=.6
t=.1 hour