Math Statistics
2008-07-10 3:54 am
Four lattices are selected from the 5 x4 grid board so that they form the corners of a rectangle having sides parallel to the edges of the board. How many different rectangles can be formed in this way?
回答 (2)
2008-07-10 8:04 pm
✔ 最佳答案
6C2 * 5C2 = 15*10 = 150
2008-07-10 5:59 am
C(6, 2) x C(5, 2) = 21 x 10 = 210。
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