Glad to see this rule come up on a tech site. This is Finance 102 stuff and it's good for everyone to know. Just in case this hasn't been said elsewhere, the

Glad to see this rule come up on a tech site. This is Finance 102 stuff and it's good for everyone to know. Just in case this hasn't been said elsewhere, the rule is more precise for numbers whose factor into 72 is closer to it. So medium numbers, for lack of a way of saying it. Not 50, not 1, but 12, 8, etc.