Problema Solution
A paddle boat can move at a speed of 10km/h in still water. The boat is paddled 6km downstream in a river in the same times it takes to go 3km upstream. What is the speed of the river?
Answer provided by our tutors
speed in still water = 10 km/h
speed of current be x
..
speed downstream = x+10
spped upstream = 10-x
...
Time = distance /speed
time upstream = 3/(10-x)
speed downstream = 6/x+10
..
the times are same
3/(10-x) =6/(x+10)
3(x+10)=6(10-x)
3x+30=60-6x
9x=60-30
3x+6x=30
9x =30
x=3.33 km/h