when andy talked about credit card numbers yesterday, it made me remember something some teacher told me once, and that is you can tell anyone's birthday by the last 5 numbers of their drivers license number.

so the first two numbers are the year the person was born in. the last three are the day number the person was born on if every month had 31 days. so what you do is use the division algorithm on the last 3 numbers to find q and r. from there, you know the person was born on the r-th day of the q+1-th month.

for example, the last five numbers of my drivers license are 87356. so i was born in 1987. using the DA, we get $356 = 11*31+15$. thus i was born on the 15th day of the 12th month (because $11+1 = 12$). so we can see that my birthday is december 15, 1987.