70%

來源: eyehalfopen 於 2010-04-27 10:03:54 [] [博客] [舊帖] [給我悄悄話] 閱讀數 : (216 bytes)

Assume A, B, C, D, E, F, G born in April
Same day with A: AB AC AD AE AF AG, 1/30 chance for each combination
Similarly:
BC BD BE BF BG 1/30
.
.
.
FG 1/30
Total: 21/30 = 70%

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