SOLUTION: Jan and Tariq took a canoeing trip, traveling 6 mi upstream against a 2 mi/h current. They then returned to the same point downstream. If their entire trip took 4 h, how fast can t

Question 287905: Jan and Tariq took a canoeing trip, traveling 6 mi upstream against a 2 mi/h current. They then returned to the same point downstream. If their entire trip took 4 h, how fast can they paddle in still water? [Hint: If r is their rate (in miles per hour) in still water, their rate upstream is r - 2 and their rate downstream is r + 2.]

Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
lettheir speed in still water be r
upstream their rate will be r-2
down stream their rate will be r+2
6/r-2 + 6/r+2 = 4
6(r+2)+6(r-2)= 4(r^2-4)
6r+12 +6r-12= 4r^2-16
4r^2-12r-16=0
4r^2-16r+4r-16=0
4r(r-4)+4(r-4)=0
(4r+4)(r-4)=0
so r=4 a positive number
they canoe at 4 mph in still water

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