📚 Year 8 WJEC Business: Quick Reference Handbook of Formulas and Theorems | 八年级 WJEC 商务：公式定理速查手册
Welcome to your essential quick-reference guide for Year 8 WJEC Business. Mastering the fundamental formulas and concepts early on will give you a solid foundation for analysing costs, revenue, profit, and break-even. This handbook groups key equations and business theorems into easy-to-scan sections, with each point presented in English followed by its Chinese equivalent so you can learn the language of business bilingually. Use it before tests, homework, or whenever you need a rapid reminder.
欢迎使用这本八年级 WJEC 商务必备速查手册。尽早掌握基本的公式和概念，将为你分析成本、收入、利润和盈亏平衡打下坚实基础。本手册将关键方程式和商业定理归入便于浏览的章节，每一点都先以英文呈现，再附中文对照，帮助你双语学习商业语言。可在测验前、做作业时或随时快速查阅。
1. Total Revenue (TR) | 总收入
Total revenue is the money a business receives from selling its goods or services. It is calculated by multiplying the price per unit by the quantity sold.
总收入是企业从销售商品或服务中获得的全部款项，用单价乘以销售数量计算。
Total Revenue = Price per unit × Quantity sold
For example, if a bakery sells 200 loaves at £1.50 each, TR = £1.50 × 200 = £300.
例如，一家面包店以每块 1.50 英镑的价格售出 200 块面包，总收入 = 1.50 × 200 = 300 英镑。
2. Total Costs (TC) | 总成本
Total cost is the sum of all expenses a business incurs in producing and selling its products. It is split into fixed costs and variable costs.
总成本是企业在生产和销售产品中发生的全部支出之和，分为固定成本和变动成本两个部分。
Total Costs = Fixed costs + Variable costs
Fixed costs do not change with output (e.g., rent), while variable costs vary directly with the number of units produced (e.g., raw materials).
固定成本不随产量变化（如租金），而变动成本直接随生产单位数变化（如原材料）。
3. Fixed Costs & Variable Costs | 固定成本与变动成本
Fixed costs remain constant regardless of how many items are made, whereas variable costs increase as production rises. Identifying these helps a business plan its budget.
固定成本无论产量多少都保持不变，而变动成本随产量增加而上升。区分它们有助于企业规划预算。
Examples of fixed costs: building rent, insurance, salaries of permanent staff.
固定成本示例：物业租金、保险费、长期员工薪酬。
Examples of variable costs: packaging, raw materials, piece-rate wages.
变动成本示例：包装材料、原材料、计件工资。
4. Total Variable Cost (TVC) | 总变动成本
Total variable cost rises in direct proportion to output. It is worked out by multiplying variable cost per unit by the number of units produced.
总变动成本与产量成正比上升，由每单位变动成本乘以生产数量计算。
Total Variable Cost = Variable cost per unit × Quantity
If making one pencil case costs £2 in materials and 300 cases are produced, TVC = £2 × 300 = £600.
若生产一个笔袋的材料成本为 2 英镑，生产 300 个，总变动成本 = 2 × 300 = 600 英镑。
5. Profit & Loss | 利润与亏损
Profit is the positive difference between total revenue and total costs. When costs exceed revenue, the business makes a loss. This simple formula underpins every business decision.
利润是总收入与总成本的正差值。当成本超过收入时，企业发生亏损。这个简单公式是每一项商业决策的基础。
Profit (or Loss) = Total Revenue − Total Costs
A profit of £500 means the business earned £500 more than it spent; a loss of £200 means it spent £200 more than it earned.
获利 500 英镑表示企业比支出多收入 500 英镑；亏损 200 英镑表示企业多花了 200 英镑。
6. Gross Profit | 毛利润
Gross profit focuses solely on the difference between sales revenue and the direct cost of goods sold (COGS). It does not include fixed overheads.
毛利润仅关注销售收入与销售直接成本（销货成本）之间的差额，不含固定营运费用。
Gross Profit = Sales Revenue − Cost of Goods Sold
If a clothing shop sells jackets for £5,000 and paid £3,000 for those jackets, its gross profit is £2,000.
如果一家服装店卖了 5000 英镑的夹克，而夹克进货成本为 3000 英镑，那么毛利润就是 2000 英镑。
7. Net Profit | 净利润
Net profit shows the final earnings after all expenses, including fixed costs and overheads, have been deducted. It is sometimes called the “bottom line”.
净利润反映扣除所有费用（包括固定成本和日常开支）后的最终收益，有时也被称为“底线利润”。
Net Profit = Gross Profit − Fixed Costs and Other Expenses
Using the earlier jacket example, if rent and wages total £800, net profit = £2,000 − £800 = £1,200.
沿用前面夹克店的例子，若租金和工资共计 800 英镑，净利润 = 2000 − 800 = 1200 英镑。
8. Profit Margin Ratios | 利润率
Margins express profit as a percentage of revenue, showing how much profit is made per pound of sales. Two key margins are gross profit margin and net profit margin.
利润率用利润占收入的百分比表示，揭示每英镑销售能带来多少利润。主要分为毛利率和净利率。
Gross Profit Margin (%) = (Gross Profit ÷ Sales Revenue) × 100
Net Profit Margin (%) = (Net Profit ÷ Sales Revenue) × 100
A 40% gross margin means 40p of every £1 sales is gross profit, before covering fixed overheads.
40% 的毛利率表示每 1 英镑销售中有 40 便士为毛利润，尚未覆盖固定开支。
9. Break-even Point (Units) | 盈亏平衡点（单位数）
The break-even point is the number of units a business must sell to cover all its costs exactly, making neither profit nor loss. It is a crucial planning tool.
盈亏平衡点是指企业刚好弥补全部成本、不赚不赔所需销售的单位数，是重要的规划工具。
Break-even Point (units) = Fixed Costs ÷ (Selling Price per unit − Variable Cost per unit)
The bottom part (price − variable cost) is called contribution per unit, showing how much each sale goes toward covering fixed costs.
分母部分（单价 – 单位变动成本）称为单位贡献毛益，表示每卖出一件能帮助覆盖多少固定成本。
10. Contribution per Unit | 单位贡献毛益
Contribution per unit is the amount left from each sale after variable costs are deducted. It first pays off fixed costs, then generates profit once break-even is passed.
单位贡献毛益是每单位销售扣除变动成本后剩余的部分，先用于支付固定成本，超过盈亏平衡点后形成利润。
Contribution per Unit = Selling Price per Unit − Variable Cost per Unit
If a smoothie sells for £3 and its ingredients cost £1.20, the contribution per unit is £1.80.
如果一杯果昔售价 3 英镑，原料成本 1.20 英镑，那么单位贡献毛益为 1.80 英镑。
11. Break-even on a Chart | 图表中的盈亏平衡
A break-even chart plots total revenue and total costs against output. The point where the two lines intersect is the break-even point. The area above shows profit, below shows loss.
盈亏平衡图将总收入和总成本随产量的变化画成折线。两条线相交的点即为盈亏平衡点，上方区域为盈利，下方为亏损。
Key elements on the chart: horizontal axis is quantity, vertical axis is costs/revenue (£), fixed cost line runs horizontally, total cost line rises from fixed cost level, total revenue line rises from zero.
图表上的关键要素：横轴为数量，纵轴为成本/收入（£），固定成本线为水平线，总成本线从固定成本线之上开始倾斜上升，总收入线从零点开始上升。
12. Cash Flow & Working Capital Theorems | 现金流与营运资金定理
Cash flow is the movement of money into and out of a business. Net cash flow for a period is simply inflows minus outflows. Positive cash flow keeps the business running.
现金流是资金流入和流出企业的运动。某一时期的净现金流就是流入减去流出。正向现金流保证企业正常运转。
Net Cash Flow = Total Cash Inflows − Total Cash Outflows
Working capital (or net current assets) measures short-term financial health: Working Capital = Current Assets − Current Liabilities. A positive figure means the business can cover its short-term debts.
营运资金（或净流动资产）衡量短期财务健康度：营运资金 = 流动资产 − 流动负债。正数表示企业有能力偿还短期债务。
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