I just got out of my math class, and we were given a problem that really, really scrambles my brain, so here it is:
Henry broke camp early and motored upriver to his favorite fishing hole. A mile upstream his hat flipped overboard, but he did not notice for another 5 minutes. As soon as he realized what happened, Henry turned around and gave chase. He came upon his hat just as it went past his camp. Assuming Henry motored at full throttle the whole time, how fast is the river flowing?