Consider the following three demand curves (where P is price in dollars and Q is quantity in units):(A) Q = 200 – P(B) Q = 100 - 0.5P(C) Q...

The price elasticity of demand is the percentage change in demand for a percentage change in price.

If the demand is Q and price is P, the price elasticity of demand at any price p is Ep = P/Q*(dQ/dP)

The first demand curve is Q = 200 - P.

dQ/dP = -1

At P = 20, Q = 200 - 20 = 180

The price elasticity of demand in this case is (20/180)*-1 = -1/9

...

The price elasticity of demand is the percentage change in demand for a percentage change in price.

If the demand is Q and price is P, the price elasticity of demand at any price p is Ep = P/Q*(dQ/dP)

The first demand curve is Q = 200 - P.

dQ/dP = -1

At P = 20, Q = 200 - 20 = 180

The price elasticity of demand in this case is (20/180)*-1 = -1/9

The second demand curve is Q = 100 - 0.5P

dQ/dP = -0.5

At P = 20, Q = 90

The price elasticity of demand is (20/90)*-0.5 = -1/9

The third demand curve is Q = 200 - 0.5P

dQ/dP = -0.5

At P = 20, Q = 190

The price elasticity of demand is (20/190)*-0.5 = -1/19