a motorboat that travels with a speed of 20 km/hour in still water has traveled 36 km against the current and 22 km with the current, having spent 3 hours on the entire trip. find the speed of the current of the river.

as you know, going with the current (downstream), the speed rate of "r" is added to boat's still water rate, and upstream is subtracted

so.. anyhow, with it, it went 36km, against it it went 22km
hmmm the time it took was 3hrs total

so, if it took "t" time going downstream, then going upstream took the difference, 3 - t

so recalling your d = rt



now.. that one doesn't have integer values...so let's run it through the quadratic formula