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1) Consider the inverse demand function for good X below PX = 30 - 0.005X + 0.15

ID: 1137155 • Letter: 1

Question

1) Consider the inverse demand function for good X below
PX = 30 - 0.005X + 0.15PY


Where X refers to the quantity of commodity X, PX and PY are the prices of good X and Y respectively. Use the point formula to calculate all elasticities.


a) Determine the value of Q when PX = 10 and PY = 100


b) Calculate the own price elasticity of demand for good X at PX = 10 and PY = 100. [Hint: use the price of good X and the quantity calculated in Part a). Also, solve for Q before taking the coefficient of PX as the Q/PX.]


c) Interpret your answer in Part b).


d) Calculate the cross-price elasticity of demand between good X and good Y at a price, PX = 10 and PY = 100. (Hint: Use the price of Y and the quantity of X calculated in Part a). Also, solve for Q before taking the coefficient of PY as the Q/PY.]


e) Interpret your answer in Part (d).

Explanation / Answer

a) Use PX = 10 and PY = 100 in the demand function

10 = 30 – 0.005QX + 0.15*100

QX = 35/0.005 = 7000 units

b) Own price elasticity of demand for good X at PX = 10 and PY = 100 is given by ed = QX/PX * PX/QX

or ex = (-1/0.005)*10/7000 = -0.286

c) Demand for good X is inelastic because the price elasticity is less than 1 in absolute terms.

d) Cross-price elasticity of demand between good X and good Y at a price, PX = 10 and PY = 100 is given by exy = QX/PY * PY/QX = (1/0.15)*(100/7000) = 0.095

e) The cross price elasticity is positive so that the two goods X and good Y are substitutes.