If the quantity supplied of a commodity increases from 20 to 30 units when there is an increase in price from N4 to N5, the elasticity of supply is

Analyze the question: We are asked to find the price elasticity of supply (PES) when quantity supplied rises from 20 to 30 units as price rises from N4 to N5.

Concept: Price elasticity of supply measures how responsive quantity supplied is to a change in price.

PES = (% change in quantity supplied) ÷ (% change in price)

Solution:

• Change in quantity = 30 − 20 = 10
• % change in quantity = (10 ÷ 20) × 100 = 50%

• Change in price = 5 − 4 = 1
• % change in price = (1 ÷ 4) × 100 = 25%

PES = 50% ÷ 25% = 2

Check with the midpoint method (just in case):

• % change in Q = 10 ÷ 25 = 40%
• % change in P = 1 ÷ 4.5 ≈ 22.2%
• PES ≈ 1.8, which is closest to 2 and not close to any other option.

So the standard JAMB approach (using the original values as the base) gives exactly 2.

Answer: C. 2. Since PES is greater than 1, supply is elastic.

Tip: In JAMB elasticity questions, use the original value as your base unless the question says "average" or "midpoint." Also, set up the formula as:

PES = (ΔQ/Q) ÷ (ΔP/P)

Write the numbers in clearly before calculating, and avoid mistakes like inverting the ratio.