📚 IB Economics Unit Test: Mastering Microeconomic Fundamentals | IB 经济单元测试卷：掌握微观经济学基础
Unit tests are a cornerstone of IB Economics preparation, helping you diagnose weaknesses before the final exams. This article presents a full-length simulated unit test covering demand, supply, elasticity, market equilibrium, and government intervention. Each question is followed by a detailed bilingual explanation so you can self-assess and deepen your understanding.
单元测试是 IB 经济备考的基石，能帮助你在最终考试前诊断薄弱环节。本文提供一套完整的模拟单元测试卷，涵盖需求、供给、弹性、市场均衡和政府干预。每道题目都配有详细的中英双语解析，方便你自评并加深理解。
1. Multiple Choice: The Law of Demand | 选择题：需求定律
Question: According to the law of demand, what will happen to the quantity demanded of a good when its price increases, ceteris paribus?
A. It will increase.
B. It will stay the same.
C. It will decrease.
D. It will first increase then decrease.
题目： 根据需求定律，在其他条件不变的情况下，当一种商品的价格上升时，其需求量会如何变化？
A. 增加。
B. 不变。
C. 减少。
D. 先增加后减少。
Answer & Explanation: The correct choice is C. The law of demand states that there is an inverse relationship between price and quantity demanded. When price rises, consumers are willing and able to buy less, so quantity demanded contracts. Options A and D contradict the law, and B would only occur if demand is perfectly inelastic, which is a special case, not the general law.
答案与解析： 正确选项为 C。需求定律指出价格与需求量呈反向关系。当价格上升时，消费者愿意且能够购买的数量减少，故需求量收缩。选项 A 和 D 违背了该定律，而 B 只在需求完全无弹性的特殊情况下才成立。
2. Multiple Choice: Movement Along vs. Shift of Demand | 选择题：需求量的变动与需求变动
Question: A fall in the price of a substitute good will cause a(n):
A. Rightward shift of the demand curve.
B. Leftward shift of the demand curve.
C. Movement down along the same demand curve.
D. Movement up along the same demand curve.
题目： 一种替代品的价格下降将导致：
A. 需求曲线向右移动。
B. 需求曲线向左移动。
C. 沿着同一条需求曲线向下移动。
D. 沿着同一条需求曲线向上移动。
Answer & Explanation: The correct option is B. A substitute’s price fall makes the substitute more attractive, so consumers switch away from the original good, decreasing its demand at every price. This is a non-price determinant, causing the entire demand curve to shift leftwards. Movements along the curve are only caused by changes in the good’s own price.
答案与解析： 正确选项为 B。替代品价格下降使其更具吸引力，消费者转而购买替代品，导致原商品的需求在所有价格水平上下降。这是非价格因素，引起整条需求曲线向左移动。沿着需求曲线的移动仅由该商品自身价格变化引起。
3. Short Answer: Calculating Price Elasticity of Demand (PED) | 简答题：计算需求价格弹性
Question: The price of cinema tickets rises from $8 to $10, and the quantity demanded falls from 1200 tickets per week to 900. Calculate the price elasticity of demand using the midpoint formula, and state whether demand is elastic or inelastic.
题目： 电影票价格从 8 美元涨至 10 美元，每周需求量从 1200 张降至 900 张。使用中点公式计算需求价格弹性，并说明该需求是富有弹性还是缺乏弹性。
Answer & Explanation: Using the midpoint formula: PED = (ΔQ/Q_avg) ÷ (ΔP/P_avg). Q_avg = (1200+900)/2 = 1050, so ΔQ/Q_avg = -300/1050 ≈ -0.2857. P_avg = (8+10)/2 = 9, so ΔP/P_avg = 2/9 ≈ 0.2222. PED = -0.2857 / 0.2222 ≈ -1.285. In absolute value, |PED| = 1.285 > 1, so demand is price elastic. A 1% rise in price leads to a 1.285% fall in quantity demanded.
答案与解析： 使用中点公式：PED = (ΔQ/Q_avg) ÷ (ΔP/P_avg)。Q_avg = (1200+900)/2 = 1050，ΔQ/Q_avg = -300/1050 ≈ -0.2857。P_avg = (8+10)/2 = 9，ΔP/P_avg = 2/9 ≈ 0.2222。PED = -0.2857 / 0.2222 ≈ -1.285。绝对值 |PED| = 1.285 > 1，因此需求是富有价格弹性的。价格每涨 1%，需求量下降约 1.285%。
4. Diagram Analysis: Market for Coffee | 图表分析：咖啡市场
Question: Draw a fully labelled market diagram for coffee. Now, suppose a frost destroys a significant portion of the coffee harvest. Explain and show on the diagram how this affects equilibrium price and quantity.
题目： 画出咖啡市场的完整标注图。现假设一场霜冻摧毁了大量咖啡收成。在图示中解释并展示这将如何影响均衡价格和数量。
Answer & Explanation: The frost reduces coffee supply (shifts supply curve left from S to S₁). Demand remains unchanged. The new equilibrium occurs at a higher price and lower quantity. In the diagram, the original equilibrium E₀ (P₀, Q₀) moves to E₁ (P₁>P₀, Q₁ 答案与解析： 霜冻减少了咖啡供给（供给曲线由 S 左移至 S₁），需求不变。新均衡点出现在更高的价格和更少的数量上。图中，原均衡 E₀ (P₀, Q₀) 转移至 E₁ (P₁>P₀, Q₁ Question: Outline two factors that make the demand for a product more price elastic. Use examples to support your answer. 题目： 简述两种使产品需求更具价格弹性的因素，并用例子支持你的回答。 Answer & Explanation: (1) Availability of close substitutes: Goods with many substitutes (e.g., breakfast cereals) have high PED because consumers can easily switch if the price rises. (2) Proportion of income: Expensive items taking up a large share of a consumer’s budget (such as cars or overseas holidays) tend to have more elastic demand, as price increases significantly affect purchasing power. By contrast, necessities with few substitutes and small budget shares (like salt) tend to be inelastic. 答案与解析： (1) 相近替代品的可获得性：拥有众多替代品的商品（如早餐麦片）其 PED 较高，因为价格上涨时消费者可轻易转向替代品。(2) 占收入的比例：占消费者预算较大的昂贵物品（如汽车或出境游）需求更富弹性，因为价格上升会显著影响购买力。相反，缺乏替代品且预算占比小的必需品（如食盐）需求往往缺乏弹性。 Question: A 5% increase in consumers’ income leads to a 10% increase in the demand for organic vegetables. The income elasticity of demand (YED) for organic vegetables is: 题目： 消费者收入增加 5% 导致有机蔬菜需求增加 10%。有机蔬菜的需求收入弹性 (YED) 为： Answer & Explanation: The answer is D. YED = %ΔQd / %ΔY = +10% / +5% = +2.0. Because YED > +1, organic vegetables are a luxury good. A negative YED would indicate an inferior good, while a positive YED less than 1 indicates a normal necessity. 答案与解析： 答案为 D。YED = %ΔQd / %ΔY = +10% / +5% = +2.0。由于 YED > +1，有机蔬菜属于奢侈品。负 YED 表明是劣等品，而介于 0 和 1 之间的正 YED 表明是普通必需品。 Question: Using a supply and demand diagram, identify the areas representing consumer surplus and producer surplus at equilibrium. Explain briefly what these areas measure. 题目： 运用供求图，标出均衡时消费者剩余和生产者剩余的区域。简要解释这些区域衡量的是什么。 Answer & Explanation: Consumer surplus is the triangular area below the demand curve and above the equilibrium price. It measures the extra satisfaction or welfare consumers receive because they pay less than what they were willing to pay. Producer surplus is the area above the supply curve and below the equilibrium price, representing the extra revenue producers earn over and above the minimum they would accept. Together, they depict total community surplus in a free market. 答案与解析： 消费者剩余是需求曲线以下、均衡价格以上的三角形区域，衡量消费者因支付价格低于其意愿支付价格而获得的额外满意度或福利。生产者剩余是供给曲线以上、均衡价格以下的区域，代表生产者获得的超过其最低可接受价格的额外收入。二者共同描绘了自由市场中的社会总剩余。 Question: Discuss the likely effects of a government imposing a maximum rent (price ceiling) below the market equilibrium in a city’s housing market. Consider consequences for different stakeholders and suggest a potential solution to any resulting problems. 题目： 论述政府对城市住房市场实行低于市场均衡的最高租金（价格上限）可能带来的影响。考虑对不同利益相关者的影响，并就任何产生的问题提出可能的解决方案。 Answer & Explanation: A price ceiling set below equilibrium creates a persistent shortage: quantity demanded exceeds quantity supplied. Tenants who find apartments benefit from lower rents, but many are unable to obtain housing. Landlords may reduce maintenance, leading to deteriorating housing quality. Black markets can emerge. One solution is a rent subsidy to low-income tenants instead of a price ceiling, which preserves the price mechanism while addressing affordability. Diagrams should illustrate the shortage and welfare loss. 答案与解析： 设定在均衡价格以下的价格上限会造成持续性短缺：需求量超过供给量。找到住房的租户因低租金受益，但许多人无法获得住房。房东可能减少维护，导致住房质量下降，黑市可能出现。解决方案之一是对低收入租户提供租金补贴，而非实行价格上限，这样既能保持价格机制又能解决可负担性问题。图中应标示短缺和福利损失。 Question: (Data provided) In 2023, the price of bananas fell by 8% while total revenue for banana producers rose by 2%. Using the data, explain what this implies about the price elasticity of demand for bananas and explain one possible reason for this. 题目： （提供数据）2023 年香蕉价格下跌 8%，而香蕉生产者的总收入上升 2%。利用数据解释这意味着香蕉的需求价格弹性如何，并说明一个可能的原因。 Answer & Explanation: When price falls and total revenue rises, demand is price elastic (|PED| > 1). The percentage increase in quantity demanded is greater than the percentage decrease in price. This could be because bananas have many close substitutes within the fruit market, or because they represent a small budget share but are often used as a staple food for price-conscious consumers. The calculated PED (ignoring sign) would be > 1. 答案与解析： 价格下跌而总收入增加，表明需求富有价格弹性 (|PED| > 1)。需求量增加的百分比大于价格下跌的百分比。可能的原因是香蕉在水果市场中有许多相近替代品，或虽预算占比小但常常作为价格敏感消费者的主食水果。不计符号的 PED 计算值将大于 1。 Key Tips: Always label axes (Price, Quantity) and curves (D, S). Distinguish clearly between ‘change in demand’ and ‘change in quantity demanded’. Use the midpoint formula unless told otherwise. For elasticity, remember that slope and elasticity are not the same. Support essay answers with real-world examples, such as sugar taxes or rent controls, and always include a well-drawn and explained diagram where relevant. 关键技巧： 始终标注坐标轴（价格、数量）和曲线（D, S）。清晰区分“需求变化”与“需求量变化”。除非另有要求，使用中点公式。对于弹性，牢记斜率与弹性并不相同。论述题答案需结合现实例子，如糖税或租金管制，并务必在相关处附上绘制清晰且解释到位的图表。 Common Mistakes: Confusing substitutes with complements when predicting shifts; forgetting to consider the ceteris paribus assumption; miscalculating percentage changes; misreading the sign of YED; and describing diagrams without linking them to economic theory. Avoid these by practicing a wide range of past paper questions and actively drawing diagrams from memory. 常见错误： 在预测变动时混淆替代品与互补品；忽略其他条件不变的假设；百分比变化计算错误；误读 YED 的正负；以及仅描述图表而未联系经济理论。通过大量练习历年试题、主动凭记忆绘制图表，可以避免这些错误。 Published by TutorHao | Economics Revision Series | aleveler.com 更多咨询请联系16621398022（同微信）
5. Short Answer: Determinants of PED | 简答题：需求价格弹性的决定因素
6. Multiple Choice: Income Elasticity of Demand (YED) | 选择题：需求收入弹性
A. -2.0
B. -0.5
C. +0.5
D. +2.0
A. -2.0
B. -0.5
C. +0.5
D. +2.0
7. Short Answer: Consumer and Producer Surplus | 简答题：消费者剩余与生产者剩余
8. Essay Question: Price Ceiling in the Rental Market | 论述题：租房市场上的价格上限
9. Data Response: The Global Banana Market | 数据分析题：全球香蕉市场
10. Exam Tips and Common Mistakes | 考试技巧与常见错误
屏轩国际教育cambridge primary/secondary checkpoint, cat4, ukiset,ukcat,igcse,alevel,PAT,STEP,MAT, ibdp,ap,ssat,sat,sat2课程辅导，国外大学本科硕士研究生博士课程论文辅导