回复：这解有点杀鸭用牛刀的味道。

来源: 于 2010-04-22 09:20:42 [旧帖] [给我悄悄话] 本文已被阅读：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.