UC知道奥数难题3
来源：百度知道 编辑：UC知道 时间：2024/05/20 00:41:42
1、Town A and town B are connected by a highway, with a service station at the midpoint. Mike and Sam start from A to B at the same time. When Mike reaches the service station, Sam is 16 km behind. Mike reduces speed by 25% after he passes through the service station. When Sam reaches the service station, Mike is 15 km ahead of Sam. What’s the distance between A and B?
Answer：
2. A large fresh water reservoir has two types of drainage system, small pipes and large pipes. 6 large pipes, on their own, can drain the reservoir in 12 hours. 3 large pipes and 9 small pipes, at the same time, can drain the reservoir in 8 hours. How long will 5 small pipes, on their own, take to drain the reservoir?
Answer： minutes
请写出过程
Answer：
2. A large fresh water reservoir has two types of drainage system, small pipes and large pipes. 6 large pipes, on their own, can drain the reservoir in 12 hours. 3 large pipes and 9 small pipes, at the same time, can drain the reservoir in 8 hours. How long will 5 small pipes, on their own, take to drain the reservoir?
Answer： minutes
请写出过程
1.设Mike速度X，Sam速度Y.
有：Y·t=16，3X/4·t=15，得X：Y=5：4 ①
再设AB距离的一半为S
有：S/Y=S/X+15/（3X/4） ②
由①②得S=80，所以AB距离为160
2.设大的X，小的Y
有：12·6X=8·（3X+9Y） 得X：Y=3：2 ①
再设时间t，有：5Y·t=6X·12 ②
由①②得t=21.6h=1296min
城A和B是连接城市的高速公路，有一个服务站的中点。迈克和山姆开始从A到B在同一时间。当小李达到了服务站，三是16公里落后。麦克减少了25 ％的速度后，他穿越了服务站。当萨姆到达服务站， 15公里的麦克是提前三。什么之间的距离A和B ？