In the midpoint method, how is the percentage change in quantity calculated between two points, Q1 and Q2?

1. The midpoint method replaces the usual base of a percentage change with the average of the two values being compared. 2. For quantity, that means Q2 minus Q1 divided by the average of Q1 and Q2, then multiplied by 100. 3. Dividing by Q1 alone, as in option C, or Q2 alone, as in option D, gives a different answer depending on which point is the starting point. 4. Reversing the numerator to Q1 minus Q2, as in option B, only flips the sign and is not how the source writes the formula. _Source: OpenStax Principles of Microeconomics for AP Courses (CC BY 4.0), Ch 5 "Elasticity", section 5.1 | Price Elasticity of Demand and Price Elasticity of Supply_