math
posted by yanyan .
a man rows downstream for one hour and 40 minutes on a river flowing at 2 miles per hour. on his returned trip he rows upstream for 5hours. find the distance that he traveled downstream and his speed of rowing in still water.

since the distance down and up is the same, if the boat's stillwater speed is s,
5/3 (s+2) = 5(s2)
s = 4
so, he rows at 4 mph in still water
the distance is thus 10 miles