prob doubt

[Sinistral]

Is it 12C3*(1/4)^3 * (3/4)^9 ?

[Gourav]

its 1      ....when n is greater than 365(for non leap year case)

for n<=365

 it is  1- none has b'day
         1-(1*364/365*363/365*......)    Why?...(first one has 365 choices.. 2nd one hs any 364    
                                                                        days...third one have 363 out of 365 days and so on....)
        =1-(364!/365^364)

[Ayushya Kaul]

According to me the answer of your last question should be:
P(only 3 correct answers)= 12C3 x 3^12/4^12

[Ayushya Kaul]

I have the same answer as yours Sinistral :)

[Ayushya Kaul]

The correct answer of the birthdday question is:
P(2 people having birthday on same day)= 1 - P(no 2 people share their birthday)
                                                       = 1- 365PN/(365)^N