<PRE><B>Question 251926</B>
D=RT
40=(R+5)T OR T=40/(R+5)
20=(R-5)T OR T=20/(R-5)
BECAUSE THE TIMES ARE THE SAME SET THESE TWO EQUATION EQUAL.
40/(R+5)=20/(R-5)
CROSS MULTIPLY
40(R-5)=20(R+5)
40R-200=20R+100
40R-20R=100+200
20R=300
R=300/20
R=15 MPH FOR THE SPEED OF THE BOAT IN STILL WATER.
PROOF:
40/(15+5)=20/(15-5)
40/20=20/10
2=2

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