When does 0.1 + 0.2 not equal 0.3? When you’re dealing with floating-point arithmetic.

Floating-point math is a complex thing to grok, but it’s important if you’re a programmer. Unfortunately, a lot of the explanations of this concept are obtuse and make your eyes glaze over. But here’s a fantastic guide that explains the important bits but in a way that everyone should be able to understand.