Re: A birthday puzzle
Alternate way of solving.
Excel Spreadsheet -- took about 2 minutes (longer to type this).
1. For each person on line, calculate the probability that there is a birthday match.
Person 1 -- 0.0000, Person 2 -- 1/365 (.00274), Person 3 2/365 (.005464) etc.
2. Determine the percentage chance that someone has not already won (this will be 1 - the sum of the probablilties determined in step 1 for all prior people).
3. For each person in line, multiply the amount in step 1 by the amount in step 2.
Relevant part of chart --
Person 19 .032207
Person 20 .03232
Person 21 .03225
Probablilities of winning increase to person 20 and decrease thereafter
|