It is similar to the problem of grocery checkout. If there are n checkout lines, the probability of being in the quickest line is 1/n, assuming that all checkouts have lines.<p>It is probably 1/(how many possible birthdays in a given year range). To be conservative (90 years): 1/90*365 or 0.003%.
1) Open browser<p>2) Navigate to <a href="https://duckduckgo.com/" rel="nofollow">https://duckduckgo.com/</a><p>3) Type in "!w birthday problem" (without the quotes)<p>4) Read the wikipedia page that appears