A pool 80 feet long, 50 feet wide, and 6 feet 8 inches deep is filled with three pipes namely: Pipe # 1 is 3 inches in diameter while pipes # 2 and # 3 are 2 inches diameter each. Through pipe # 1 a flow of 180 gal / min of water is supplied, through pipe # 2, 8 ft3 / min and through the third a total of 18 m3 / hour. In the filling process, the valve of pipe # 1 is opened first, one hour later the valve of pipe # 2 opens and half an hour after opening the second one opens # 3. In how long will 90% of the total pool capacity be completed?
