IGCSE Maths: Number, Ratio and Percentages (G-1 Teacher’s Resource 600) | IGCSE 数学：数、比与百分比（G-1 教师用书 600）

📚 IGCSE Maths: Number, Ratio and Percentages (G-1 Teacher’s Resource 600) | IGCSE 数学：数、比与百分比（G-1 教师用书 600）

This revision guide covers the essential skills in IGCSE Mathematics for working confidently with numbers, ratios, percentages, and proportional reasoning. These topics appear frequently on both Core and Extended papers, often in real-life contexts such as shopping, finance, measurement, and travel. Understanding these foundations is vital for success across the entire IGCSE Mathematics syllabus.

本复习指南涵盖 IGCSE 数学中处理数、比、百分比和比例推理的核心技能。这些主题在 Core 和 Extended 试卷中频繁出现，常用于购物、金融、测量和旅行等实际情境。掌握这些基础对于整个 IGCSE 数学课程的成功至关重要。

1. Integers and Order of Operations | 整数与运算顺序

Always apply the order of operations: Brackets, Indices, Division and Multiplication (left to right), Addition and Subtraction (left to right). Many students lose marks by working from left to right without considering priority.

始终按照运算顺序计算：括号、指数、除法与乘法（从左到右）、加法与减法（从左到右）。许多学生因没有考虑优先级而丢分。

BIDMAS: Brackets → Indices → Division/Multiplication → Addition/Subtraction | 括号 → 指数 → 除法/乘法 → 加法/减法

For example, calculate 3 + 4 × 5. Multiplication comes first, so 4 × 5 = 20, then add 3 to get 23, not 35.

例如，计算 3 + 4 × 5。先算乘法，4 × 5 = 20，再加 3 得到 23，而不是 35。

Brackets force priority: (3 + 4) × 5 = 7 × 5 = 35. Indices mean powers: 2³ = 2 × 2 × 2 = 8. When division and multiplication appear together, work from left to right.

括号强制优先级：(3 + 4) × 5 = 7 × 5 = 35。指数表示乘方：2³ = 2 × 2 × 2 = 8。当除法和乘法同时出现时，从左到右计算。

2. Fractions, Decimals and Percentages | 分数、小数与百分比

Fractions, decimals and percentages are three ways of representing the same proportion. You must be able to convert between them quickly and accurately.

分数、小数和百分比是表示同一比例的三种方式。你必须能够快速准确地在它们之间进行转换。