SOLUTION: Jen's boat cruised 45 miles upstream and 45 miles back in a total of 6 hrs. The speed of the river is 2 mph. Find the speed of the boat in still water.

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Question 241694: Jen's boat cruised 45 miles upstream and 45 miles back in a total of 6 hrs. The speed of the river is 2 mph. Find the speed of the boat in still water.

Answer by scott8148(6628) About Me  (Show Source):
You can put this solution on YOUR website!
[45 / (b-2)] + [45 / (b+2)] = 6

multiplying by (b-2)(b+2) ___ 45b + 90 + 45b - 90 = 6b^2 - 24

0 = 6b^2 - 90b - 24

dividing by 6 ___ 0 = b^2 - 15b - 4

use quadratic formula to find b