72 - Rule of 72

Finance shortcut for doubling-time estimates.

Why this number matters

72 is useful for understanding number patterns, powers, factors, and how math ideas connect in real examples.

Background / history

Mathematicians and teachers have used numbers like 72 to explain structure, patterns, and numeric relationships.

Simple example

A quick way to sanity-check 72: 24 + 48 = 72. You can also test divisibility (for example, 72 is divisible by 2).

Key Facts

Fun fact

72 is a composite number.

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