Q.Identify and explain the following concepts:
40% fall in price of a commodity leads to 40% rise in quantity demanded.

The Percentage (Proportionate) Method applies $E_d=\dfrac{\Delta Q}{\Delta P}\times\dfrac{P}{Q}$ directly to a before-and-after price-quantity pair, using the ORIGINAL price and quantity as the base. The Total Outlay (Total Expenditure) Method, given by Marshall, needs no formula: it reads elasticity off how total expenditure (Price × Quantity) moves when price changes — outlay moving OPPOSI …