Question

If the demand function for a good is Q=140 – 5P, what is the price elasticity of demand at P = 

15 rupees?

Answer 1

$Q=140-5P, \space P=15 rupees$

$Q=140-5\times15=65\space rupees$

$E_d=\frac{dQ}{dP}\times \frac{P}{Q}=-5\times\frac{15}{65}=-1.15$