中等ECON-ELAS-008
If the cross elasticity of demand between goods X and Y is -2, then a 5% increase in the price of X will cause the quantity demanded of Y to:
A. Decrease by 10%✓ 答案
B. Increase by 10%
C. Decrease by 2.5%
D. Increase by 2.5%
解說
Cross elasticity of demand = %ΔQd of Y ÷ %ΔP of X. Since cross elasticity is -2 (X and Y are complements), %ΔQd of Y = -2 × 5% = -10%, so the quantity demanded of Y decreases by 10%. B has the wrong sign; C and D have the wrong magnitude (they would follow if the elasticity were -0.5).