When price of a commodity falls by Rs. 1 per unit, its quantity demanded rises by 3 units. Its price elasticity of demand is `(-)2`. Calculate its quantity demanded if the price before the change was Rs. 10 per unit.

Explanation

`{:(" PED" =[-]2" Given"),("Price before change [Initial Price] P = 10 Initial Quantity "(Q)=?),("New Price "[P_(1)]=9 " New Quantity " (Q_(1))=?),(Delta P=-1" [Given] " Delta Q=3):}`
`PED=(Delta Q)/(Delta P)xx(P)/(Q) " or " (-)2=(3)/((-)1)xx(10)/(Q)`
`Q=(30)/(2)=15`
So, the quantity demanded at price before change [P], i.e., 10, is equal to 15.