What is Percentage? — Mathematics

Definition 44.6 Primary & Middle School Mathematics · Chapter 44 — Proportionality and Data

“ $t\,\%$ of a quantity” means the fraction $\frac{t}{100}$ of it: $25\,\%$ of $60$ is $\frac{25}{100} \times 60 = 15$ . A percentage is a proportionality with coefficient $\frac{t}{100}$ .

Examples

Example 44.7

A class of $30$ students contains $40\,\%$ girls. Number of girls, step by step: $40\,\%$ means $\frac{40}{100} = 0.4$ , and $0.4 \times 30 = 12$ girls. Useful landmarks: $50\,\%$ is one half, $25\,\%$ one quarter, $10\,\%$ one tenth — so $10\,\%$ of $30$ is $3$ , and $40\,\% = 4 \times 10\,\%$ is $4 \times 3 = 12$ : same answer, computed mentally.

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