when the price is is rs 5 per unit a consumer buys 40 unit of a commodity and his price elasticity of demand is - 1.5 how much will he buy if the prices reduced to rs 4 per unit

We have, Ed = -1.5
P = 5
Q = 40
∆P = 4-5 = -1
Ed = (P÷Q) × (∆Q÷∆P)
-1.5 = (5÷40) × {∆Q ÷ (-1)}
∆Q = (40×1.5) ÷5 = 12
Q1 - Q = 12
Q1 - 40 = 12
Q1 = 52
Hence, the new quantity demanded is 52 units.