Fred paddled for 5 hours with a 6kmhr current to reach a cam

Fred paddled for 5 hours with a 6km/hr current to reach a campsite. The return trip against the same current took 10 hours. Find the speed of Fred\'s canoe in still water.

Solution

Let x = velocity in still water
.
Distance = Velocity * Time
.
D1 = (x+6) 5 = 5x +30
.
D2 = (x-6) 10 = 10x -60
.
but D1 = D2
.
5x +30 = 10x -60
.
90 = 5x
.
18 = x
.
checking
.
(18 +6) * 5 = (18-6) 10
.
120 =120,,,,ok