机经一篇[转帖]

smart

2003-3-26, 武汉。
考的不是很理想。几道JJ.
AWA: issue:No.21, argument:NO.28
Math:
1. 一个正方形ABCD， 在外面有一点E, CE=1,并且BE=DE. 求三角形BEC的面积。
2. There are 5 cars, 3 in red, 1 in blue and 1 in white. If all the cars are the same except the color, and now they are to be arranged facing the wall. There are how many ways to arrange them?
思路：P5/P3. The least number is 20. so I chose the answer: 20.
3. A pile of boxes, the bottom layer has 9*9 boxes, and each layer has one row less and one less in column than the layer under it. The upper layer has 1 box. How many boxex are there in total?
思路：1^2+2^2+3^2+...+9^2=