1、如图（1），将一个长为a，宽为b的长方形(a＞b)沿虚线剪开，拼成图（2），成为在一角去掉一个小正方形的大正方形，则小正方形的边长为（    ）

A     B  a-b   C     D 

 2、某同学想用5个边长不等的正方形，拼成如图所示的大正方形，请问该同学的想法能实现吗？

A   能        B   否

3、MN表示某引水工程的一段设计路线，从M到N的走向危南偏东30⁰，再M的南偏东60⁰方向上有一点A，以A为圆心，500m为半径的圆形区域为居民区，取MN上另一点B，测得BA的方向为南偏东75⁰，已知MB=400m，cot30⁰=1.732，通过计算回答，如果不改变方向，输水线路是否会穿过居民区？

4、Mr King was the manager of a hotel.One weekend all the hotels in the city were full because there was a large meeting. On Friday night, three men came into the hotel and asked for rooms.Mr King said there were no rooms ready because of the meeting.The men were a bit angry.

Mr King wanted to help them. He remembered that Room 418, a very small room,was empty.He asked them if they would share a room.The three men said OK.Mr King said the room would be thirty dollars:ten for each one. Each man gave him the money and then they went upstairs.Mr King soon began to fell sorry.“Thirty dollars is a lot to ask as price for that small room, “he through. He called his assistant over and said,“Here is five dollars. Take it to the men in Room 418. I asked too much for their room.”

  While the assistant was on the way upstairs,he started to think with the money,“How can three men do with the five dollars? I’’ll give them each only one dollar and keep the two dollars for myself. The men will be happy to get something back, and Mr King will never know.”So the assistant gave each man one dollar.

  At first each man paid ten dollars. After the assistant gave them back one dollar each, they each paid nine. There were three men, $9*3= $27.The assistant kept $2. $27+$2=$29.Where is the missing dollar?