2986/5625 (~0.5308)

来源: 于 2010-05-25 12:20:09 [博客] [旧帖] [给我悄悄话] 本文已被阅读：次

30 days in April.
7 students born in April.
1-30x29x28x27x26x25x24/30**7
=1-29x13x7/5x5x15x15
=1-2639/5625
=2986/5625
=0.53084444444444444......