







When is John's next birthday on a Friday? 
20190315 

From Darek: The question is the following:
Last Friday 4th of April of 2014 John was 40 years old. How old will John be the next time when his birthday fell on Friday?
Thanks for your help Answered by Penny Nom. 





Today is Emma's Birthday. 
20120125 

From Mike: Today is Emma's Birthday.
Emma's mother is four times as old as Emma is today.
In four years, Emma's mother will be three times as old as Emma.
How old is Emma today? Answered by Penny Nom. 





Probability and birthdays 
20090122 

From La: Neglecting the effect of leap years, what is the chance that, of 6 people selected at random, 2 will have the same birthday? Answered by Penny Nom. 





What year were the girls born in? 
20080106 

From Nyra: Christmas 2004 was over and three teenagers were looking forward to their birthdays. Eric's was in February and Lisa's and Tammy's in January. Tammy is 8 weeks older than Eric, but 3 days younger than Lisa. What year were the girls born in? Answered by Claude Tardif. 





Your birthdays until your one hundredth 
20060909 

From Alan: which of your birthdays until your one hundredth, fall on the same day of the week as the day you were born? Answered by Chris Fisher. 





Zhi Wei was born on christmas day in 1983. 
20060214 

From Clement: Zhi Wei was born on christmas day in 1983. His father shares the same birthday, but he was born in 1951. In which year will Zhi Wei's age be exactly 1/3 of his father's age? Answered by Stephen La Rocque. 





Unusual occurances 
20040108 

From Martin: My wife and I have a question about the probability of something that happened to us a few years ago. So far, no one has been able to give me even an approximate answer. On my 32nd birthday, my wife and I went out to eat at local Japanese hibachi style restaurant. At the restaurant, couples/families are sat together around the hibachi where the cook performs a show. There was a fifteen minute or so wait, so my wife and I sat in the lounge waiting for our name to be called. When they called our names for the reservation, this is what happened. The first group called was the Martin family. Then they called the Francis family. We were the next family to be called, the Ashton family. My full name is Martin Francis Ashton! I think the odds of that happening to someone are very unlikely, but it did, and there is more. Next, we were all sat at the same table in that order, "Martin" family, "Francis" family, then us, the "Ashton" family. Again, it formed my full name! Answered by Penny Nom. 





I can Guess your birthday 
20030829 

From Michelle: Hi I am trying to explain to my children how this problem works. It was sent to me on the internet and I can not figure it out. They keep asking me how it works and I can not tell them. The problem is: "I can Guess your birthday:: Answered by Penny Nom. 





The birthday problem 
19990419 

From Gordon Cooke: How do I explain the rapid rise in the probability that at least two people in a group of n have the same birthday. We have derived the formula for p(n) and have graphed it and have seen how the results are counterintuitive. At around n=23 p(n)=.5 and at n=50 p(n) is very close to 1. It does not help to simplify the problem (eg use months instead of days) because then our intuition does correspond more closely to reality. Is there some way we can see how the probabiltiy of a "collision" increases with n? It makes me think of data storage problems and hash tables in computer science. Answered by Harley Weston. 





The Birthday Problem 
19980612 

From Josh Skolnick: if you are at a party what is the least amount of people that have to be there to have at least a 50% chance of having 2 people with the same birthday? and how do you get the answer thank you in advance josh Answered by Harley Weston. 

