Percentages

Japanese school year: Elementary 5

What you learn

You will learn the meaning of percentages as ratios regarding the base quantity as 100, along with the percent symbol. This concept is commonly used when calculating discounts, growth rates, and statistical data. A clear grasp of decimal operations and basic ratios provides a strong foundation.

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Key points

This formula is used to convert a decimal ratio $p$ into a percentage $R$ (in $\%$ ). Multiplying ratio $p$ by $100$ scales the value to a base of $100$ .

R = p \times 100

This formula is used to convert a percentage $R$ back into a decimal ratio $p$ for calculations. Dividing the percentage $R$ by $100$ yields the decimal form.

p = \frac{R}{100}

This formula is used to find the quantity $a$ that corresponds to $R\%$ of a base total $b$ . Multiply the base amount $b$ by the fraction $\frac{R}{100}$ .

a = b \times \frac{R}{100}

This explains how percentages work. The reference base is set to $100\%$ , so the percentage can exceed $100\%$ when an amount has increased from the original.

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Practice 1Coming soon