现有一台天平，一个2克的砝码和一个7克的砝码，要求只使用这台天_爱下问搜题

搜题请搜索小程序“爱下问搜题”

问题解答题

现有一台天平，一个2克的砝码和一个7克的砝码，要求只使用这台天平三次，将一包重140克的食盐分成90克和50克。此外，为了便于减少误差，每次分离食盐时，规定重量是整数千克。请你设计尽可能多的方案，说明基本理由。

答案

此题有多种答案。若考虑现有砝码与其不同放置的情况，可将指定重量分为2份，它们的重量之差(克数)仅限于：0、2、5、7与9。因此可设如下数学模型：

从而可得下 * * 种解决方案

而若考虑将已称量的食盐当作新的砝码，则还可以得到其他的解决方案（“略”）。

完形填空

I tend to accept any idea put forward by experts on TV. One day, a sociologist(社会学家) proposed that the   36 society has been consuming modern humans little by little. For fear that I would become a victim of the consumer society, I   37 hurried to a bicycle shop in my neighborhood.   38  the shopkeeper Mr. Johnson was selling me the bicycle, he said, “This is the best thing you   39  have done. Life has become hopelessly   40 . A bicycle is simple, and it brings to you   41  things: fresh air, sunshine and exercise.” I agreed. Happy as a child, I got on the bicycle and headed out onto the streets. After some time, I   42  at the other end of the town. I was   43  that this simple vehicle could let me   44 long distances in a fairly short time. But how   45  did I really go?
Since I hated to be   46 , I went back to Mr. Johnson and asked him to   47  an odometer (里程表) on my bicycle. He agreed, but   48 , “An odometer without a speedometer (速度计) is like a   49  without a knife.” I admitted he was right and in a few minutes, the two devices (装置) were   50 to the handlebars of my bicycle. “What about a horn?” he then asked. “Look, this horn is no larger than a matchbox and has many   51 .” Attracted by these functions, I bought the horn.
“You can’t leave the back part   52 ,” noted Mr. Johnson. He fixed a metal box with buttons   53 the seat, and said, “Is there anything better than this oven(烤箱) when you feel   54 on your way? I can give you a special discount.” I was not strong enough to   55  the offer.
“I congratulate you once more; this is the best thing you could have done,” said Mr. Johnson in the end.

B．immediately

C．reluctantly

B．complicated

C．calmed down

B．impractical

A．distributed

单项选择题

国际性组织顶级域名为（）。

A、int

B、org组织

C、net机构

D、com商业