An empty swimming pool with a capacity of 5,760 gallons is filled by a pipe at the rate of 12 gallons per minute

题目

An empty swimming pool with a capacity of 5,760 gallons is filled by a pipe at the rate of 12 gallons per minute. There is an emptying pipe which, in 9 hours, can empty the pool, which is full. How many hours does it take to fill the pool, which is already half filled, if both the pipes are kept open?

选项

解析

选项B。注水效率 = 12加仑/分钟排水效率计算：泳池内水量 = \(5760 \times \frac{2}{4} = 4320\) 加仑排空所需时间 = \(9 \times 60 = 540\) 分钟 → 排水效率 = \(4320 \div 540 = 8\) 加仑/分钟若泳池为半满状态，剩余需注水量 = \(5760 \div 2 = 2880\) 加仑总效率 = \(12 - 8 = 4\) 加仑/分钟 → 所需时间 = 720分钟，即 \(720 \div 60 = 12\) 小时

在线客服

官方微信

公众号