Planet Money Episode 544: The M&M Anomaly

One day we noticed something strange: a pack of Milk Chocolate M&M's weighs 1.69 ounces, but a pack of Peanut Butter M&M's weigh a tiny, tiny bit less, 1.63 ounces. The two packs are the same price, but you get slightly less of the Peanut Butter M&M's! 0.06 ounces less! It turns out there is a whole weird world living down there at the third decimal place. When you pull on that little thread, lots of things start to unravel.