Question

Difficulty: MediumCardinal Utility Analysis and Consumer Equilibrium

A consumer purchasing two goods, XX and YY, attains equilibrium when the marginal utility of Good XX (MUxMU_x) is 4040 utils and its price (PxP_x) is 10\text{₦}10. If the price of Good YY (PyP_y) is 5\text{₦}5, what is the marginal utility of Good YY (MUyMU_y) in utils at consumer equilibrium?

Answer: 20 utils / 20 / 20utils

Answer

The marginal utility of Good YY at consumer equilibrium is 20 utils.
Under cardinal utility analysis, consumer equilibrium for two commodities is achieved when the ratio of marginal utility to price is equal for both commodities (MUxPx=MUyPy\frac{MU_x}{P_x} = \frac{MU_y}{P_y}). Substituting MUx=40MU_x = 40, Px=10P_x = 10, and Py=5P_y = 5 gives 4010=MUy5\frac{40}{10} = \frac{MU_y}{5}, which simplifies to 4=MUy54 = \frac{MU_y}{5}. Solving for MUyMU_y gives 2020 utils.

Step-by-Step Solution

1
State the equimarginal condition for consumer equilibrium when consuming two goods.
MUxPx=MUyPy\frac{MU_x}{P_x} = \frac{MU_y}{P_y}
According to cardinal utility analysis, a consumer maximizes utility when the marginal utility per monetary unit spent is equal across all commodities.
2
Substitute the given values (MUx=40MU_x = 40, Px=10P_x = 10, Py=5P_y = 5) into the formula.
4010=MUy5\frac{40}{10} = \frac{MU_y}{5}
Substituting the known parameters sets up an algebraic equation for the unknown marginal utility of Good YY.
3
Solve the equation for MUyMU_y.
4=MUy5    MUy=4×5=20 utils4 = \frac{MU_y}{5} \implies MU_y = 4 \times 5 = 20\text{ utils}
Multiplying the marginal utility per naira spent (4 utils/naira) by the price of Good YY (₦5) gives the marginal utility of Good YY.

Key Concept

Equimarginal Principle of Consumer Equilibrium
Estimated Time:1m 30s
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