Price (₦) Quantity Demanded 8 10 6 12 If we move from 8 to 6, the elasticity of demand is_______

Analyze the question: Price falls from ₦8 to ₦6, and quantity demanded rises from 10 to 12. We need the price elasticity of demand.

Concept: Price elasticity of demand (PED) = % change in quantity demanded ÷ % change in price.

There are two common ways to calculate it:

Method 1: Simple percentage change (starting point as base)

• % change in quantity = (12 − 10)/10 × 100 = +20%
• % change in price = (6 − 8)/8 × 100 = −25%
• PED = 20 / −25 = −0.8, so the magnitude is 0.8

Method 2: Midpoint (arc) formula

• % change in Q = 2 / 11 = 0.1818
• % change in P = −2 / 7 = −0.2857
• PED = 0.1818 / −0.2857 ≈ −0.64

Which matches the options?

• Method 1 gives 0.8, which matches option C exactly.
• The midpoint method gives about 0.64, which is close to B (0.62) but not exact.
• Option A (−1.25) is the inverse (25/20), which comes from putting the percentages the wrong way round.
• Option D (1) does not match anything.

The JAMB approach for this kind of question uses the basic formula with the original values as the base, so the answer is 0.8 (the negative sign is usually dropped, since demand curves slope downward and we quote elasticity as a magnitude).

Conclusion: Since 0.8 < 1, demand is inelastic over this price range.

Tip: In JAMB elasticity questions, use the formula PED = (ΔQ/Q) ÷ (ΔP/P) with the original (starting) values unless the question mentions "average" or "midpoint." If you get the reciprocal of your answer among the options (like 1.25 here), that's a trap for those who flip the formula. Remember: quantity on top, price at the bottom.