aarondfrancis

"Picked up 3 quarters from my spare change pile. They were all from 1984. What are the 
chances?!?!" [http://d.pr/9Trc]

So first, we need to figure out how many quarters in any given pile should be dated 1984. 
Let's say that there are 65 billion quarters in circulation at the moment [1] and that 
there were 1.2 billion quarters minted in 1984 [2].

That means that 1.85% of the quarters in a given pile should be quarters with the date 
1984. [1.2/65 = 1.85%]