Suppose the price elasticity of demand for a good is (-)1. At a price of ₹4 per unit, demand for the good is 40 units. Suppose the price of the good increases to ₹6 per unit, and as a result, the demand for the good will be ____________.

20 units

The correct answer is option (2) : 20 units

$P_1=4,P_2=6$

$Q_1=40,Q_2=?$

$ΔP=P_2-P_1=6-4=2$

$ΔQ=Q_2-Q_1$

$e_D=-1$

$e_D=\frac{ΔQ}{ΔP}×\frac{P_1}{Q_1}$

$-1=\frac{ΔQ}{2}×\frac{4}{40}$

$-1=\frac{ΔQ}{20}$

$ΔQ=-20$

$Q_2-Q_1=-20$

$Q_2=-20+Q_1$

$Q_2=-20+40=20$