



 
Hi Paul, You don't know the speed of the river so I am going to call it s mph. Thus, going with the current, downstream, the speed of the boat is (30 + s) mph and going upstream, against the current, the speed of the boat is (30  s) mph. At (30 + s) mph how long does it take to go 100 miles? These two times are the same. Solve for s. Penny  


Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences. 