Worksheet Answers – Chapter 21 | 第21章练习题答案解析

📚 Worksheet Answers – Chapter 21 | 第21章练习题答案解析

This article provides model answers and clear explanations for the typical questions found in the Chapter 21 worksheet of the Cambridge International AS & A Level Business syllabus. The chapter centres on inventory (stock) management, stock control charts, re‑order levels, buffer stock, Just‑in‑Time (JIT) and the costs linked with holding stock. Each section matches a key learning objective and shows you how to construct high‑scoring answers.

本文为剑桥国际A Level商务第21章练习题提供范例答案与详细解析。本章重点涵盖库存管理、库存控制图、再订货水平、缓冲库存、准时制生产以及持有库存的相关成本。每一个小节对应一项核心考点，并展示如何组织高分回答。

1. Defining Inventory and Its Main Types | 库存定义及主要分类

Inventory (or stock) refers to the materials and goods a business holds as part of its operations. In a manufacturing business, inventory is typically divided into three categories: raw materials, work‑in‑progress (semi‑finished goods) and finished products. A worksheet question often asks students to distinguish between these three types. A strong answer will not only define them but also give clear examples from a manufacturing context — for instance, steel, engines being assembled and completed cars in an automobile factory.

库存（即存货）指企业为运营而持有的物料与货品。在制造企业中，库存通常分为三类：原材料、在制品（半成品）和产成品。练习题中常要求学生区分这三种类型。高质量的回答不仅要给出定义，还需结合制造业实例加以说明——例如汽车工厂中的钢材、正在组装的发动机和已完工的汽车。

Raw materials: inputs purchased from suppliers that have not yet entered production.
Work‑in‑progress: goods partially completed on the production line.
Finished goods: completed products ready for sale to customers.

原材料：从供应商处购入、尚未进入生产环节的投入品。
在制品：生产线上部分完工的半成品。
产成品：已完成并可销售给顾客的最终产品。

A common application question asks: “Why might a firm wish to hold high levels of finished goods stock?” The answer should mention seasonal demand, wanting to meet unexpected orders and the ability to smooth production throughout the year.

常见的应用题会问：“企业为何希望持有较多产成品库存？”答题时需提及季节性需求、能满足突发订单以及全年均衡生产的能力。

2. Reading a Stock Control Chart | 解读库存控制图表

Stock control charts are a graphical tool that shows how inventory levels move over time between deliveries. The worksheet often presents a simplified chart and asks you to label or explain the maximum stock level, re‑order level, minimum stock level (buffer stock) and lead time. A model answer must show you understand not just the definitions but also what the chart tells a manager. For example, a steep downward slope suggests rapid usage rate, while a gentle slope may indicate slow‑moving items.

库存控制图是一种图形工具，展示两次交货之间库存水平随时间变化的轨迹。练习题常给出简化的控制图，要求标注或解释最高库存量、再订货水平、最低库存量（缓冲库存）和前置时间。完整的答案不仅要给出定义，还要说明该图能向管理者传达什么信息。例如，陡峭的下降线段表明物料消耗速率快，平缓的线段则说明商品周转慢。

Key elements to describe in your answer include the saw‑tooth pattern (gradual usage followed by a sudden replenishment) and the fact that the re‑order level must be set high enough to cover demand during the lead time. If the worksheet asks “What happens if the re‑order level is set too low?”, you should explain that the inventory line will fall below the minimum stock level, or even break through zero, leading to a stock‑out.

回答时需描述锯齿状图形（逐渐消耗后突然补货），并指出再订货水平必须足够覆盖前置期内的需求。若题目问“再订货水平设置过低会怎样”，则应说明库存线将跌破最低库存线，甚至突破零库存，导致缺货。

3. Calculating the Re‑order Level | 再订货水平的计算

Many Chapter 21 worksheets contain a calculation exercise based on the formula:
Re‑order level = Maximum usage × Maximum lead time.

第21章练习题常包含基于公式的计算题：再订货水平 = 最大用量 × 最大前置时间。

Suppose a firm uses up to 400 units of a component per week and the longest delivery time from its supplier is 3 weeks. The re‑order level is:
400 × 3 = 1,200 units.

假设企业每周最多消耗某种零件400件，供应商最长交货时间为3周，则再订货水平为：400 × 3 = 1200件。

A fuller answer should note that using maximum figures helps build a safety margin inside the re‑order point itself. If the question asks “Why should the business also consider average usage?”, you can explain that using maximum figures all the time might lead to holding excess stock, which ties up working capital unnecessarily.

更完整的回答应指出，使用最大值能在再订货点内部构建安全边际。若问题问“为何企业还要考虑平均用量”，则可解释始终使用最大数据可能导致持有过多库存，不必要地占用营运资金。

4. Buffer Stock and Its Role | 缓冲库存及其作用

Buffer stock (safety stock) is the inventory kept on hand in case demand is higher than expected or a delivery is delayed. The worksheet may contain a scenario where a business is considering reducing its buffer stock; you are then asked to discuss the pros and cons. An effective answer acknowledges that cutting buffer stock releases cash and reduces storage costs, but it also makes the firm more vulnerable to stock‑outs, possible production stoppages and damage to customer goodwill.

缓冲库存（安全库存）是为应对需求超预期或交货延迟而持有的备用量。练习题可能给出某企业考虑降低缓冲库存的情景，要求讨论利弊。有效的回答需认识到，减少缓冲库存能释放现金、降低仓储成本，但也使企业更易遭遇缺货、可能造成生产停滞并损害客户好感度。

In an evaluation question, you should mention that the optimal level of buffer stock depends on the reliability of suppliers, the accuracy of demand forecasts and the cost of a stock‑out relative to the cost of holding inventory. For a hospital holding life‑saving drugs, a high buffer is essential; for a grocery store selling daily‑demand bread, a lower buffer is acceptable.

在评估类题目中，应提到最优缓冲库存水平取决于供应商可靠性、需求预测精度以及缺货成本相对于持有库存成本的大小。对储备救命药品的医院而言，高缓冲库存不可或缺；对销售日常面包的便利店而言，较低缓冲量便可接受。

5. Costs of Holding Stock | 持有库存的成本

The worksheet frequently asks students to identify and explain different costs that arise from holding inventory. These costs can be classified as:

练习题常要求学生识别并解释持有库存产生的不同成本，这些成本可分为以下几类：

Storage costs: rent of warehouse space, heating, lighting, insurance and security.
Opportunity cost: money tied up in stock could have been used elsewhere in the business or earned interest.
Obsolescence and wastage: goods may become out‑of‑date, perish or go out of fashion.
Administrative costs: stock‑taking, IT systems and staff needed to manage inventory.

仓储成本：仓库房租、暖气、照明、保险及安保费用。
机会成本：积压在库存中的资金本可用于企业其他用途或赚取利息。
过时与损耗：货品可能过期、腐坏或不再流行。
管理成本：盘点、信息技术系统及管理库存所需的人力。

When the worksheet presents a case study of a business with high inventory levels, a strong recommendation often involves analysing the trade‑off: holding more stock reduces the risk of stock‑out but increases these holding costs. Always support your points with application from the case, such as specific percentage increases in storage fees.

当练习题给出库存水平较高的案例，有力的建议通常涉及权衡分析：持有较多库存虽能降低缺货风险，但会增加上述各项成本。回答时务必结合案例信息（如仓储费用上涨的具体百分比）来支撑观点。

6. Stock‑out Costs | 缺货成本

Equally important are the costs of holding too little inventory. A worksheet question might ask: “Explain two costs to a business of running out of stock.” A model answer would include:

同样重要的是持有过少库存的代价。练习题可能问：“解释企业缺货所产生的两类成本。”范例答案可包含：

Lost sales and reduced revenue: customers who cannot buy the product may go to a competitor and may not return.
Damaged brand image and customer loyalty: repeated stock‑outs create a reputation of unreliability.
Production downtime: in a factory, missing a single raw material can halt the entire production line, raising idle‑time costs.
Emergency purchasing costs: ordering last‑minute supplies often means paying premium prices and express delivery fees.

销售损失与收入减少：买不到商品的顾客可能转向竞争者，且不会再度光顾。
品牌形象与客户忠诚度受损：频繁缺货会形成不可靠的声誉。
生产停工：在工厂中，缺少一种原材料便可导致整条生产线停顿，产生闲置时间成本。
紧急采购成本：最后一刻下单往往要支付溢价价格和加急运费。

7. Just‑in‑Time (JIT) Production Explained | 准时制生产解析

JIT is a lean production method that aims to hold zero (or very minimal) inventory by ensuring materials arrive exactly when they are needed for production or sale. In a Cambridge worksheet, a typical definition question expects you to mention that JIT requires close relationships with reliable suppliers, efficient production scheduling and a flexible, multi‑skilled workforce.

准时制是一种精益生产方式，力求通过确保物料恰好在生产或销售所需之时到达，实现零库存（或极低库存）。在剑桥练习题中，典型的定义题会期望你提到，JIT要求与可靠供应商建立紧密关系、高效的生产排程以及灵活的多技能员工队伍。

An application question might provide data on a bakery that switched from keeping large flour stocks to daily deliveries from a local mill. Your answer should highlight reduced storage costs and less wastage of perishable ingredients, but also note the risk if the mill’s lorry breaks down — production could stop the same day.

应用题可能给出某面包店的数据，它由存放大批量面粉改为由当地磨坊每日送货。答题时需强调仓储成本下降和易腐原料浪费减少，但同时指出风险——若磨坊货车抛锚，当天即会停产。

8. Advantages and Disadvantages of JIT | 准时制的优势与劣势

Many worksheet questions require an evaluation of JIT. Use a balanced approach. Below is a table that can be used to structure a 10‑mark discuss question.

许多练习题要求对JIT进行评述，需采用平衡论述方式。下方表格可帮助构建一道10分讨论题的结构。

Advantages 优势	Disadvantages 劣势
Reduced storage and insurance costs 仓储与保险费用降低	High dependence on supplier reliability; any delivery failure stops operations 高度依赖供应商可靠性；任何交货失误即导致停产
Less working capital tied up in stock, improving liquidity 减少库存占用的营运资金，改善流动性	Loss of bulk‑buying discounts; can increase unit costs 丧失批量采购折扣，可能推高单位成本
Smaller defects because problems are spotted quickly and waste is visible 缺陷更少，因为问题能被迅速发现、浪费显而易见	Requires a flexible, multi‑skilled workforce and a different organisational culture 需要灵活多技能的劳动力和不同的组织文化
Encourages continuous improvement and lean culture 鼓励持续改善和精益文化	May be unsuitable for businesses with highly seasonal or unpredictable demand patterns 可能不适用于需求高度季节性或不稳定的行业

In a conclusion, weight up the circumstances. For an electronics manufacturer with dependable local suppliers, JIT can bring significant cost savings. For a small retailer in a remote area with long supply lines, JIT risks doing more harm than good.

在结论中需权衡具体情形。对于有可靠本地供应商的电子制造商，JIT可带来显著成本节约；而对地处偏远、供应链较长的小型零售商，JIT或许弊大于利。

9. Economic Order Quantity (EOQ) – Formula and Worked Example | 经济订货量——公式与例题

Occasionally, Chapter 21 worksheets introduce the EOQ model to find the optimum number of units to order at one time, balancing ordering costs and holding costs. The formula is:

EOQ = √(2 × D × O / C)

其中 D = annual demand in units, O = ordering cost per order, C = holding cost per unit per year.

D 为年需求量（件），O 为每次订货成本，C 为每件年持有成本。

If a firm uses 10,000 units of a raw material each year, the cost of placing one order is $50, and the annual holding cost per unit is $2.50, then:

若企业每年使用某原料10,000件，每次订货成本为50美元，每件年持有成本为2.50美元，则：

EOQ = √(2 × 10,000 × 50 ÷ 2.50) = √(1,000,000 ÷ 2.50) = √400,000 ≈ 632 units.

A top‑grading worksheet answer would not only compute the EOQ but also comment that the model assumes constant demand and immediate replenishment, which rarely holds exactly in real life. You might add that the EOQ helps to guide order quantities but should be adjusted for bulk discounts or shelf‑life constraints.

高分答卷不仅会算出EOQ，还会指出该模型假设需求恒定且即时补货，现实中几乎不会完全满足。你还可补充，EOQ有助于指导订货批量，但需根据批量折扣或保质期限制加以调整。

10. Analysing a Scenario: Should the Business Reduce Its Re‑order Level? | 情景分析：企业是否应降低再订货水平？

In the final worksheet section, you may face a longer evaluative question such as “Evaluate the proposal to reduce the re‑order level from 800 to 600 units.” Start by calculating the impact: with a maximum usage of 200 units per week and a lead time of three weeks, the new re‑order level just about covers demand in normal conditions (3 × 200 = 600). However, if lead time stretches to four weeks or demand spikes to 250 units, a stock‑out will occur. Lowering the re‑order level reduces the average stock held, thereby cutting holding costs and freeing cash. But the risk of disappointed customers and lost sales from even one stock‑out could outweigh those annual savings. A justified conclusion might recommend keeping the re‑order level at 800 for high‑margin items with unpredictable demand, while cautiously lowering it for low‑value components with stable usage.

在练习题的末尾部分，你可能会遇到较长的评估题，比如“评估将再订货水平从800件降至600件的提议”。先计算影响：周最大用量200件，前置时间3周，新的再订货水平在正常情况下刚好能满足需求（3×200=600）。但若前置期延长到4周或需求突增至250件，缺货便会发生。降低再订货水平会减少平均库存，从而削减持有成本并释放现金。但哪怕一次缺货所引发的客户流失和销售损失，也可能超过年度节省额。一个有说服力的结论可建议：对于利润率高、需求不稳定的品项，维持800件的再订货水平；而对用量稳定、价值较低的物料，可谨慎下调。

11. Common Mistakes to Avoid in Chapter 21 Answers | 第21章答题常见误区

Students often lose marks by confusing re‑order level with buffer stock, or by treating the re‑order level as a fixed number without linking it to usage and lead time. Another frequent error is describing JIT simply as ‘holding no stock’, without explaining the conditions needed to make it work. Additionally, when faced with calculation questions, many forget to state the unit of measurement in the final answer (e.g. ‘632 units’). Always show your working and relate the numerical result back to the business context.

学生常见的丢分点是将再订货水平与缓冲库存混淆，或者将再订货水平视作一个固定数字，而未联系用量与前置时间。另一个常犯错误是只把JIT描述为“不持库存”，却不解释其所需的条件。此外，计算题中许多人忘记在最终答案中写明单位（如“632件”）。务必展示计算过程，并将数字结果回扣到商业情境中。

12. Summary of Key Takeaways | 重点总结

A complete mastery of Chapter 21 enables you to analyse stock‑holding strategies under different scenarios. Remember that there is rarely a single ‘right’ inventory level — the answer depends on the business environment, product characteristics and management priorities. When you tackle a worksheet question, always define the key term, apply given data, discuss both costs and benefits, and finish with a balanced, well‑justified recommendation. This structure will consistently earn high marks in Cambridge A‑Level Business exams.

全面掌握第21章，便能根据不同情景分析库存持有策略。请记住，几乎没有绝对“正确”的库存水平——答案取决于商业环境、产品特性和管理层优先事项。当应对练习题时，请始终遵循：定义关键术语，结合给定数据，讨论成本与收益，最后以兼顾各方、理由充分的建议作结。这样答题结构定能在剑桥A‑Level商务考试中稳定获取高分。

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Worksheet Answers – Chapter 21 | 第21章练习题答案解析