SOLUTION: A motorboat can go 8 miles downstream on a river in 20 minutes. It takes 30 minutes for this boat to go back upstream the same 8 miles. Find the speed of the current.

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 Click here to see ALL problems on Expressions-with-variables Question 309206: A motorboat can go 8 miles downstream on a river in 20 minutes. It takes 30 minutes for this boat to go back upstream the same 8 miles. Find the speed of the current.Answer by checkley77(12569)   (Show Source): You can put this solution on YOUR website!D=RT 8=R*20 R=8/20 R=2/5 OR .4 MPM. DOWNSTREAM RATE 8=R*30 8=30R R=8/30 R=4/15 OR .267 MPM. UPSTREAM RATE. (.4-.267)/2=.133/2=.067 MPM IS THE RATE OF CURRENT. 8=(R+.067)20 8=20R+1.34 20R=8-1.34 20R=6.66 R=6.66/20 R=.333 SPEED OF THE BOAT. 8=(R-.067)30 8=30R-2.01 30R=8+2.01 30R=10.01 R=.333 SPEED OF THE BOAT.