Math & Statistics

What Is a Logarithm?

A logarithm answers the question: to what power must a base be raised to produce a given number? For example, log base 10 of 1,000 is 3, because 10³ = 1,000. Logarithms turn multiplication into addition and are used to solve for time in growth problems.

Common Bases

Base 10 (common log), base e ≈ 2.718 (natural log, written ln), and base 2 (used in computing).

A Practical Use

The time needed to double money at rate r is ln(2) ÷ ln(1 + r), which the rule of 72 approximates.

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🔗 Related Terms

Exponent Exponential Growth Rule of 72 Scientific Notation

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Last updated: September 29, 2026. This definition is for general educational purposes only. It is not financial, investment, tax, legal, or medical advice, and it does not recommend any product or course of action. For decisions about your own situation, consult a qualified professional.