回複：這解有點殺鴨用牛刀的味道。

來源: 於 2010-04-22 09:20:42 [舊帖] [給我悄悄話] 本文已被閱讀：次

A: the area is defined by x=0, y=0, x=60, y=60, y=x-20 and y=x+20.
B: the area is defined by x=0, y=0, x=60, y=60.
The probability = A/B = 5/9.