Riffling from factory order to complete randomness.You’ve probably seen a few ways to shuffle a deck of cards. Sometimes the deck is split in half and the halves are switched. Sometimes the deck is smooshed until it’s all mixed up. But most of the time, a deck of cards is shuffled using a riffle.Here’s a question: how many times do you have to riffle a deck of cards before it is completely shuffled? It’s a tricky one, but math has us covered: you need seven riffles. We can calculate the number o...