This problem, birthday paradox, involves some derivations using ln and e. Fortunately google directed me to a site called www.betterexplained.com where the author has explained about this problem, the constant e and ln in very simple terms. This is the first time that I enjoyed learning some math stuff and understood something intuitively. The website name certainly stands for its content. The author is not math professsional. He is just a computer science undergrad and working somewhere now. Many thanks to him for his brilliant work and few to Google for giving me the link to this site. :)
If you wanna know more about e and ln, go through the below links. I am sure it would be useful by some means.
There are lot more math and other general stuff posted on this website. Have to go through them in my leisure time.
p.s. Still I have a hunch that tells me at least 2 or 3 guys from my class would know ln and e very well in our undergraduation itself if not in schoolings. One of my probable for this list is Shankar. Hope my hunch would be true.