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Jim paddles from one shore of a lake three miles wide at 4 mph, and John paddles from the opposite shore at 5 mph. Speed = 4 +5 = 9 mph ,distance covered = 3 miles ,time = distance/speed = 3/9 =1/3 *60 = 20 minutes. They will meet after 20 minutes.
Added 4/16/2020 12:15:20 PM
This answer has been confirmed as correct and helpful.