<PRE><B>Question 732255</B>
D=RT
24=(R-4)T OR T=24/(R-4)
40=(R+4)T OR T=40/(R+4)
SET THESE TWO EQUATIONS EQUAL;
24/(R-4)=40/(R+4) CROSS MULTIPLY.
40(R-4)=24(R+4)
40R-160=24R+96
40R-24R=96+160
16R=256
R=256/16
R=16 MPH. IS THE SPEED OF THE BOAT IN STILL WATER.
PROOF:
24/(16-4)=40/(16+4)
24/12=40/20
2=2</PRE>