At Least Once Probabilities

Question

You walk into a room with 3 other people in it. What is the probability that one or more of them has a birthday in the same month as yours?



??? (Round to the nearest tenth of a percent.)

Answer 1

Hi Mirian,

 

Ok so the probability of the people not having the birthday is 11/12

 

and we can then multiply that 3 times for each person

 

11/12*11/12*11/12 = 1331/1728

 

.77 or 77%  (this is the probability that none of the three will have  a birthday in the same month

 

so the probability that at least one of them will is 1 minus this number

 

1 - .77 = .23

 

23%  (probability that one of the 3 will have a birthday in the same month

 

Hope this helps