IGCSE Mathematics: Mastering Percentages and Compound Interest | IGCSE 数学：掌握百分数与复利

📚 IGCSE Mathematics: Mastering Percentages and Compound Interest | IGCSE 数学：掌握百分数与复利

Percentages appear throughout the IGCSE Mathematics syllabus, from basic percentage of an amount to compound interest and reverse percentage problems. This revision guide brings together the essential methods and the most common exam-style applications so that you can work confidently, with or without a calculator.

百分数贯穿 IGCSE 数学考纲，从基础的“求一个数的百分之几”到复利与反向百分数问题都会出现。本复习指南整合了核心方法与最常见的考试应用，帮助你无论是否使用计算器都能自信作答。

1. Percentages as fractions and decimals | 百分数、分数与小数的互化

A percentage is simply a fraction with denominator 100: 35% means 35/100. To convert a percentage to a decimal, divide by 100, so 35% = 0.35. To convert a decimal to a percentage, multiply by 100, so 0.175 = 17.5%.

百分数本质上是以 100 为分母的分数：35% 表示 35/100。把百分数化为小数时除以 100，因此 35% = 0.35；把小数化为百分数时乘以 100，因此 0.175 = 17.5%。

If a quantity is given as a fraction, convert it to a percentage by multiplying by 100%. For example, 7/20 = (7 ÷ 20) × 100% = 35%.

如果给出的数量是分数，则乘以 100% 化为百分数。例如 7/20 = (7 ÷ 20) × 100% =

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