JAMB 2017 Economics · Question 2

Given that Qd = 10 - 2p while Qs = 5 + 3P, if P = N 1 determine the equilibrium quantity

Options

Answer: D. 8

Explanation written with AI and checked against the answer key

Analyze the question: We are given a demand function and a supply function, and asked for the equilibrium quantity. The wording "if P = N1" is a bit awkward, so let's solve it properly and then check it. Concept: Equilibrium occurs where Qd = Qs. Step 1: Find the equilibrium price 10 - 2P = 5 + 3P 10 - 5 = 3P + 2P 5 = 5P P = 1 So the equilibrium price is N1, which matches the given P = N1. The wording simply confirms the equilibrium price. Step 2: Find the equilibrium quantity Substitute P = 1 into the demand function: Qd = 10 - 2(1) = 8 Check with the supply function: Qs = 5 + 3(1) = 8 Both give 8, so the market clears at a quantity of 8. Answer: The equilibrium quantity is 8, which is option D. Tip: When the question gives the price, substitute it into both equations. If Qd = Qs, you have confirmed equilibrium, and that common value is the equilibrium quantity. If they don't match, the given price is not the equilibrium price. In a typical JAMB question, you can also solve Qd = Qs first to find P, then substitute back to find Q.

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