Answer:
-1.15
Explanation:
the arc elasticity of demand is calculated by dividing % change in quantity demanded by % change in price:
midpoint Q = (8 + 18) / 2 = 13
midpoint P = (0.50 + 1) / 2 = 0.75
% change in quantity demanded = (Q2 – Q1) / midpoint Q = (8 – 18) / 13 = -0.77
% change in price = (P2 – P1) / midpoint P = (1 – 0.5) / 0.75 = 0.67
PED = -0.77 / 0.67 = -1.15