KS3 CIE Business: Formula & Theorem Quick Reference Guide | KS3 CIE 商务：公式定理速查手册

📚 KS3 CIE Business: Formula & Theorem Quick Reference Guide | KS3 CIE 商务：公式定理速查手册

This quick reference guide covers the essential formulas and key economic theorems you need to master for KS3 CIE Business. Use it to revise calculations for revenue, costs, profit, break‑even, ratios, productivity, cash flow, and the fundamental laws that shape business decisions. Every formula is presented in a clear, bilingual format to support your learning.

这本速查手册涵盖了 KS3 CIE 商务课程必须掌握的核心公式与重要经济定理。你可以用它复习收入、成本、利润、盈亏平衡、财务比率、生产率、现金流量等计算方法，以及影响商业决策的基本定律。所有公式均以清晰的中英双语对照呈现，方便学习。

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1. Revenue, Cost and Profit | 收入、成本与利润

Revenue is the money a business earns from selling goods or services. Costs are the expenses of production, split into fixed costs (e.g. rent) and variable costs (e.g. raw materials). Profit is the reward for taking risks – it is what remains after all costs have been deducted from revenue.

收入是企业销售商品或服务获得的收入。成本是生产中的花费，分为固定成本（如租金）和变动成本（如原材料）。利润是对承担风险的回报——它是从收入中扣除所有成本后的余额。

Total Revenue (TR) = Selling Price per Unit × Quantity Sold

总收入 = 单位售价 × 销售量

Total Costs (TC) = Fixed Costs + (Variable Cost per Unit × Quantity)

总成本 = 固定成本 + (单位变动成本 × 数量)

Profit = Total Revenue – Total Costs

利润 = 总收入 – 总成本

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2. Break-Even Point and Contribution | 盈亏平衡点与贡献

The break‑even point is where total revenue equals total costs – the business makes no profit and no loss. Contribution helps to pay off fixed costs first; it is the amount left from each sale after covering variable costs.

盈亏平衡点是指总收入等于总成本的位置——企业既不盈利也不亏损。贡献首先用于弥补固定成本；它是扣除变动成本后每笔销售留下的金额。

Contribution per Unit = Selling Price – Variable Cost per Unit

单位贡献 = 售价 – 单位变动成本

Break‑Even Output (units) = Fixed Costs ÷ Contribution per Unit

盈亏平衡产量（单位） = 固定成本 ÷ 单位贡献

Total Contribution = Contribution per Unit × Quantity Sold

总贡献 = 单位贡献 × 销售数量

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3. Margin of Safety | 安全边际

Margin of safety shows how much sales can fall before the business reaches its break‑even point. A high margin of safety means lower risk of making a loss.

安全边际显示销售额可以下降多少才会达到盈亏平衡点。安全边际高意味着亏损的风险较低。

Margin of Safety (units) = Current or Planned Output – Break‑Even Output

安全边际（单位） = 当前或计划产量 – 盈亏平衡产量

Margin of Safety (%) = (Margin of Safety ÷ Current Output) × 100

安全边际率 (%) = (安全边际 ÷ 当前产量) × 100

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4. Gross and Net Profit Margins | 毛利率与净利率

Profit margins tell us how much profit a business makes for every £1 of sales. Gross profit margin focuses on direct costs, while net profit margin includes all expenses.

利润率表示企业每 1 英镑销售收入能获得多少利润。毛利率只关注直接成本，净利率则包含所有费用。

Gross Profit = Revenue – Cost of Sales

毛利 = 收入 – 销售成本

Gross Profit Margin (%) = (Gross Profit ÷ Revenue) × 100

毛利率 (%) = (毛利 ÷ 收入) × 100

Net Profit Margin (%) = (Net Profit ÷ Revenue) × 100

净利率 (%) = (净利润 ÷ 收入) × 100

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5. Working Capital and Current Ratio | 营运资金与流动比率

Working capital measures whether a business can pay its short‑term bills. Liquidity ratios tell the same story in percentage terms. Both use current assets and current liabilities.

营运资金衡量企业是否有能力支付短期账单。流动比率则以比例形式反映同一情况。两者都使用流动资产和流动负债。

Working Capital = Current Assets – Current Liabilities

营运资金 = 流动资产 – 流动负债

Current Ratio = Current Assets ÷ Current Liabilities (expressed as a ratio, e.g. 1.5:1)

流动比率 = 流动资产 ÷ 流动负债（以比率表示，如 1.5:1）

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6. Acid Test (Quick) Ratio | 速动比率

The acid test ratio is a stricter measure of liquidity because it removes inventory – the least liquid current asset – from current assets.

速动比率是更严格的流动性衡量指标，因为它从流动资产中剔除了流动性最差的存货。

Acid Test Ratio = (Current Assets – Inventory) ÷ Current Liabilities

速动比率 = (流动资产 – 存货) ÷ 流动负债

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7. Average Cost | 平均成本

Average cost shows the cost of producing a single unit. It helps a business set prices and understand economies of scale.

平均成本显示生产一个单位产品的成本。它有助于企业定价和理解规模经济。

Average Cost = Total Costs ÷ Output

平均成本 = 总成本 ÷ 产量

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8. Labour Productivity | 劳动生产率

Labour productivity measures how efficiently workers turn inputs into outputs. Higher productivity can lower average costs.

劳动生产率衡量工人将投入转化为产出的效率。更高的生产率可以降低平均成本。

Labour Productivity = Total Output ÷ Number of Employees

劳动生产率 = 总产量 ÷ 员工人数

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9. Cash Flow – Net Cash Flow | 现金流量 – 净现金流量

Cash flow is the movement of money in and out of a business. Net cash flow simply shows whether more cash came in or went out during a period.

现金流量是指资金进出一个企业的流动。净现金流量则显示某一时期是现金流入多还是流出多。

Net Cash Flow = Total Cash Inflows – Total Cash Outflows

净现金流量 = 总现金流入 – 总现金流出

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10. Law of Demand and Supply | 供需定律

The law of demand states that, ceteris paribus, when the price of a good rises, the quantity demanded falls. The law of supply states that, ceteris paribus, when the price rises, the quantity supplied rises. Together they determine the market price and quantity traded.

需求定律指出，在其他条件不变的情况下，商品价格上升，需求量下降。供给定律指出，在其他条件不变的情况下，价格上升，供给量上升。二者共同决定市场价格和交易量。

Key relationships:

关键关系：

• Demand: P ↑ → Qd ↓ (inverse relationship)
• 需求：价格上升 → 需求量下降（反向关系）
• Supply: P ↑ → Qs ↑ (direct relationship)
• 供给：价格上升 → 供给量上升（正向关系）

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11. Opportunity Cost | 机会成本

Opportunity cost is the value of the next best alternative foregone when a choice is made. It is a fundamental economic concept that reminds us every decision involves a trade‑off.

机会成本是指做出选择时所放弃的下一个最佳选择的价值。它是一个基本的经济概念，提醒我们每个决策都涉及权衡取舍。

For example, if a business invests £10,000 in new equipment instead of a marketing campaign, the opportunity cost is the potential extra sales lost from not marketing.

例如，如果一家企业将

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