# SOLUTION: Debbie traveled by boat 5 miles upstream to fish in her favorite spot. Because of the 4-mph current, it took her 20 minutes longer to get there than to return. How fast will her bo

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 Click here to see ALL problems on Radicals Question 186087: Debbie traveled by boat 5 miles upstream to fish in her favorite spot. Because of the 4-mph current, it took her 20 minutes longer to get there than to return. How fast will her boat go in still water?Answer by ankor@dixie-net.com(15646)   (Show Source): You can put this solution on YOUR website!Debbie traveled by boat 5 miles upstream to fish in her favorite spot. Because of the 4 mph current, it took her 20 minutes longer to get there than to return. How fast will her boat go in still water? : Let s = boat speed in still water then (s-4) = speed upstream and (s+4) = speed down stream : Convert 20 min to hrs: 20/60 = hr : Write a time equation: time = Upstream time = downstream time + 20 minutes (1/3 hr) = + : To clear out these denominators, multiply equation by 3(s+4)(s-4) 3(s+4)(s-4)* = 3(s+4)(s-4)* + *3(s+4)(s-4) Results in : 15(s+4) = 15(s-4) + (s+4)(s-4) : 15s + 60 = 15s - 60 + s^2 - 16 : 0 = 15s - 15s - 60 - 60 + s^2 - 16 : 0 = s^2 - 136 : s^2 = 136 s = s = 11.66 mph speed in still water : : Check solution on calc: (speed up = 7.66 and speed down = 15.66) 5/7.66 - 5/15.66 = .3333 which is 1/3 of an hr