If you’re serious about investing, you have to develop a head for math. Hard numbers not only keep you grounded, but sometimes offer the only way to make sense of the weird ways that Wall Street works. Consider that odd fact I shared recently about how a 50% loss followed by a 50% gain actually leaves you 25% in the hole . Strange, but true! And here’s another fun fact: In a room of just 23 people there’s a 50/50 chance that two people share the same birthday. In a room of 40 people, the chance is more than 90%… And at 55, the chance is 99%.… Read more