2006-10-08 12:33:34 · 7 answers · asked by Char 1 in Science & Mathematics ➔ Mathematics
If you're asking the probability of two people having a birthday on the 13th of a specific month, say October, then it's (1/365)^2.
If you're asking the probablity of two people having a birthday on the 13th of the same month (but it doesn't matter which month), then it's (12/365)(1/365). The first person has 12 changes, but the second must have the same as the first.
If you're asking the probablity of two people having a birthday on the 13th of the month (but it doesn't have to be the same month), then it's (12/365)^2.
This all ignores leap day. If you want to include that, then the 365's above all become 365.25.
2006-10-08 12:44:17 · answer #1 · answered by Steve A 7 · 3⤊ 0⤋
Depends on the month. Let's say a month has 30 days. The chances of each person being born on any specific single day is 1 in 30. Therefore:
1/30 X 1/30 = 1/900
2006-10-08 19:44:56 · answer #2 · answered by Rick 2 · 0⤊ 0⤋
There are 12 "thirteenth" days in a year.
Hence the probability would be = 12/365
2006-10-08 19:40:29 · answer #3 · answered by Calculus 5 · 1⤊ 0⤋
My brother's birthday's on the 13th of August.
2006-10-08 19:41:02 · answer #4 · answered by Katlyn ♥ Disney 6 · 0⤊ 1⤋
12/365 * 12/365 = .0010809
2006-10-08 19:46:19 · answer #5 · answered by bob h 3 · 0⤊ 0⤋
i dont get it... any ways, my friends birthday is on may 13th
2006-10-08 19:41:52 · answer #6 · answered by kgl 2 · 0⤊ 0⤋
very rare.
2006-10-08 19:36:53 · answer #7 · answered by conde_c_b 7 · 0⤊ 1⤋