Sep 13, 2006
Birthday Matches
Sep 13, 2006
I'm reading a book "Math Wonders to inspire teachers and students"
There are many interesing facts about math such as this:
Let us suppose you have a class wit 35 students, what do you think the chances are of the two students having the same birth date?
It's not as low as our intuition make us think. It's about 80%!
The solution is:
The probability that one selected matches his own birth date is, of course, 1 (Or it can be written as 365/365)
The probability that another student does not match the first student is
(365-1)/365 = 364/365
The probability that the third student doses not match the firstand the first student is
(365-2)/365 = 363/365
The probaility of all 35 students not having the same birth date is:
p = (365/365)*(364/365)*(363/365)*...*(331/365)
So, our answer to the question is
q = 1-p
~0.814
:)
and if the number of the students is 60 the answer is 0.994!
Unbelievable, isn't it?
2 comments:
hey, it's scientific,
which can be proof.
from the rule of probability,
how special???
:P
ieieie...
p.s. it's kindergarten mathmatics
(if you have any problem
contact me as the given number)
emm,
moreover, when i read back again,
i think i'm always a bit distracted
from the point you want to tell.
am i?
hihi~~ i hope not(not so much).
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