Show that if there are 100,000,000 wage earners in the US who earn less then 1,000,000 dollars, then there are two who earned exactly the same amount of money, last year:

There are 8 digits in the possible wage so the number of possible wages are 99,999,999 wages. If everyone had a different possible wage then we could only have 99,999,999 different wages. However in the problem we have 100,000,000 wage earners. We have to assign the last wage earner a wage that is exactly the same as the another wage earner.