The other day some friends and I came across a job posting for ITA Software on the T. It read:
If the integers from 1 to 999,999,999 are written as a word, and concatenated, what is the 51 billionth letter?
The eight of us spent the duration of the ride discussing this question and its solutions. This inspired me to write
Integer#to_word for Ruby, as part of one possible way to solve it.
From the tutorial:
> 999999.to_word => "nine hundred ninety nine thousand nine hundred ninety nine"