In microeconomics, what do we call goods that are typically consumed together, such that an increase in the consumption of one leads to a rise in the demand for the other?

Introduction / Context:
Understanding the relationship between goods is an essential part of microeconomics and consumer theory. Some goods are related in such a way that they are used together, while others can replace each other. These relationships affect how demand changes when prices or incomes change. The question focuses on the category of goods that are consumed together, like tea and sugar or car and fuel, and asks for the correct term used in economics to describe them.

Given Data / Assumptions:

• We are looking at goods that are consumed together, not separately.
• Examples include items like shoes and shoelaces, printer and ink, or car and petrol.
• The options include inferior goods, normal goods, complementary goods, and substitute goods.
• We assume standard microeconomic definitions of these terms.

Concept / Approach:
Complementary goods are goods that are used together in consumption. When the use of one increases, the demand for the other tends to rise because they jointly provide utility. Substitute goods, in contrast, can replace one another; an increase in the price of one makes the other more attractive. Normal goods are goods for which demand rises when consumer income increases, and inferior goods are goods for which demand falls when income rises. The phrase “consumed together” directly matches the definition of complementary goods, and this relationship is often represented by a negative cross price elasticity of demand.

Step-by-Step Solution:
Step 1: Identify the key phrase in the question: goods that are consumed together.Step 2: Recall that complementary goods are defined as goods that are jointly consumed, such that consumption of one increases the usefulness of the other.Step 3: Recognise that when the consumption of one complementary good rises, demand for the other good also tends to increase because both are used together.Step 4: Note that inferior and normal goods describe how demand changes with income, not how two goods are related to one another in joint consumption.Step 5: Substitute goods are alternatives, not goods consumed together; they are used instead of each other.Step 6: Therefore, the correct term for goods consumed together is complementary goods.

Verification / Alternative check:
Consider some simple examples. If a consumer buys a car, the demand for petrol rises because the car and petrol are used together. If the price of petrol becomes very high, people may reduce their car usage, affecting demand for both goods. Similarly, buying a printer increases demand for ink cartridges. These examples clearly illustrate goods that are consumed together and are discussed in textbooks under the heading of complementary goods. This confirms that complementary goods is the correct label for the concept in the question.

Why Other Options Are Wrong:
Inferior goods (option A) are goods for which demand falls when income rises; this is unrelated to whether the goods are consumed together with another good. Normal goods (option B) simply have demand that increases with income; again, this does not specify a relationship between two different goods. Substitute goods (option D) are alternatives that consumers switch between, not goods used jointly. Only complementary goods (option C) correctly describe goods that are usually consumed together.

Common Pitfalls:
A frequent error is to confuse complementary and substitute goods because both involve relationships between products. The key is to remember that complementary goods go together, while substitutes replace each other. Another pitfall is ignoring the direction of the demand response: for complements, a fall in the price of one tends to increase demand for the other, while for substitutes, a rise in the price of one increases demand for the other. Keeping these distinctions clear helps answer such definitional questions accurately.

Final Answer:
Goods that are consumed together are called Complementary goods.