This question appears simple but it is not.
The simplistic approach goes as follows:
But at step 1 you have ignored Leap Years. At step 2 you assume that the day of the week for the 13th is independent from one month to another. This is not true: for example, in a non Leap Year, February and March must be the same. In fact. in the 20th Century, the 13th fell on Fridays more than any other day of the week. However, it is possible, though tedious, to adjust for both these factors but there are others which make the task virtually impossible:
Births are not uniformly distributed across the year. In the UK, for example, in the 36 years from 1979 and 2014 (inclusive), the 13th did not feature in any year as the most popular date of birth. With only 34 years that is not too extreme. However, if the date was approximately evenly distributed, you would expect the most popular day to lie in the range 10-16 around 8 times in 34 years. In fact, this happened only once!
The most popular day to be born was Friday, followed very closely by Thursday, Wednesday, and Tuesday. Mondays tended to have fewer births than other weekdays. Saturdays and Sundays have even fewer births. The lower figures for the weekends may be due to management decisions not to schedule planned births, such as caesarean sections at weekends when fewer staff are available. This may have a bunching effect of Fridays.
So you are faced with 13 being less common but Fridays being more so. Disentangling that requires some very serious data crunching!
Depending on the year, the number of Friday the 13ths range from 1 to 3. The number of days in a year can be 365 or 366 if it is a leap year. Take the number of Friday the 13ths and divide by the number of days in the year. For example, the probability for 2009 is 3/365 to be born on Friday the 13th.
the devil came to earth and thats how friday the 13th was born
The probability of two people's birthday being the same is actually more likely than many would think. The key thing is to note that it doesn't matter what the first person's birthday is. All we need to work out is the probability that the second person has a birthday on any specific day. This probability is 1/365.25 The probability that they were born on June 10th is 1/365.25. The probability that they were born on February 2nd is 1/365.25 and the probability that they were born on the same day as you is 1/365.25
364 out of 365
2018 will be the eighth time since 1964 that the 13th of April falls on a Friday. The other years were 1973, 1979, 1984, 1990, 2001, 2007, and 2012.
Depending on the year, the number of Friday the 13ths range from 1 to 3. The number of days in a year can be 365 or 366 if it is a leap year. Take the number of Friday the 13ths and divide by the number of days in the year. For example, the probability for 2009 is 3/365 to be born on Friday the 13th.
Well..., first you have to be born on the 13th of some month. But your birth-day has to be 13 years before a Friday the 13th in the same month. So the probability is low. It also depends on the month you were born. A very lucky,..AND TRUE..., example is my 13th birthday. I'll turn 13 on Friday the 13th of July in 2012. So...I'm rare. LOW PROBABILITY!!
There are currently about 5 million people alive that were born on Friday the 13th, and increasing.
the devil came to earth and thats how friday the 13th was born
Yes, Taylor Swift was born on Friday December 13th 1989
Friday........my husband was born Friday 13th, 1978!
June... June 13th 1946 it can't be in June 13th 1946 , the 13th wasn't a Friday it was a Thursday
Yes February 13 1976 was a Friday. My little sister was born on Friday the 13th. haha.
In this year 2012 their are three Fridays the 13th. On January, on April and on July.Assuming an almost constant daily birth rate for all of the days of the year, the fraction of people born on a Friday the 13th would be: 3/366 = 1/122 == 8.196721311... x 10-3 ≈ 0.0081967 ≈ 0.0082 ≈ 0.82%.
Natalia is 17 yrs. old. Her birthday is Jan. 13. She was born on Friday the 13th
if we assume that the probability for a girl being born is the same as a boy being born: (1/2)^6 = 0.015625 = 1.5625%
1 out of 7 I think so!