Question 250972
D=RT
R=D/T
(R+3)(R-3)8=2*45
8(R^2-9)=90
8R^2-72=90
8R^2=90+72
8R^2=162
R^2=162/8
R^2=20.25
R=SQRT20.25
R=4.5 MPH IS THE SPEED OF THE BOAT IN STILL WATER.
PROOF:
(4.5+3)(4.5-3)*8=2*45
7.5*1.5*8=90
90=90