Growth's Secret Formula

The number e (about 2.71828) is the constant of continuous growth. Compound $1 at 100% interest once and you get $2. Compound it more and more often, and the value never quite reaches $2.71828 — that limiting value is e.

Every process that grows or decays smoothly follows it: populations, radioactive atoms, cooling coffee, investment returns. Over the next few cards you will see where e comes from, why its own slope equals itself, and the famous equation that ties it to pi.