严格求解: 0.4833716386560448

严格求解:
{ P(30,6)*C(7,2) + P(30,5)*C(7,3) + P(30,4)*C(7,4) + P(30,3)*C(7,5) + P(30,2)*C(7,6) + P(30,1)*C(7,7) } / { P(30,7) + P(30,6)*C(7,2) + P(30,5)*C(7,3) + P(30,4)*C(7,4) + P(30,3)*C(7,5) + P(30,2)*C(7,6) + P(30,1)*C(7,7) }

把下列数字 copy&paste 到 https://www.suresome.com 的计算机(Real-Time Universal Calculator)中, 即得0.4833716386560448:

(30*29*28*27*26*25*7*6/2 + 30*29*28*27*26*7*6*5/3/2 + 30*29*28*27*7*6*5*4/4/3/2 + 30*29*28*7*6*5*4*3/5/4/3/2 + 30*29*7*6*5*4*3*2/6/5/4/3/2 + 30)/(30*29*28*27*26*25*24 + 30*29*28*27*26*25*7*6/2 + 30*29*28*27*26*7*6*5/3/2 + 30*29*28*27*7*6*5*4/4/3/2 + 30*29*28*7*6*5*4*3/5/4/3/2 + 30*29*7*6*5*4*3*2/6/5/4/3/2 + 30)

所有跟帖： 

• 回复：严格求解: 0.4833716386560448 -jinjing- ♀ (94 bytes) () 05/08/2010 postreply 14:55:07

• 回复：回复：严格求解: 0.4833716386560448 -芷娞- ♀ (16 bytes) () 05/08/2010 postreply 15:24:36

• You are right! I am a mathmatician and statistician -noname100- ♂ (0 bytes) () 05/14/2010 postreply 17:00:16