17. An empty swimming pool can be filled in 18 hours. If the pool is full, it takes 72 hours to drain it. How long will it take to fill the empty pool with the drain left open?
If the drain is left open, the pool will fill at 3/4 the normal rate. 1/4 of 18 equals 4.5 hours. The pool would take about 4.5 hours longer to fill. The answer is 22.5 hours
