Question 280396
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