Debbie traveled by boat 5 miles upstream to fish in her favo

Debbie traveled by boat 5 miles upstream to fish in her favorite spot. because of the 6-mph current, it took her 20 minutes longer to get there than to return. How fast will her boat go in still water?

Solution

Upstream Data:
distance=5miles; rate=boat speed - current= b-6 mph; time=5/(b-6)
Downstream Data:
distance=5mils; rate=boat speed + current= b+6 mph; time= 5/(b+6)
EQUATION:
Upstream time - (1/3)hr = Downstream time
5/(b-6)- (1/3)=5/(b+6)
5(3)(b+6)-(b+6)(b-6)=5(3)(b-6)
15b+90-[b^2-36]=15b-90
b^2-216=0
b=14.697mph
boatspeed in still water is 14.697mph