The formula for computing price elasticity of demand is :

$\left(\frac{Q}{ΔQ}\right)×\left(\frac{ΔP}{P}\right)$ $\left(\frac{ΔP}{ΔQ}\right)×\frac{P}{Q}$ $\left(\frac{ΔQ}{Q}\right)×\left(\frac{P}{ΔP}\right)$ $\left(\frac{ΔQ}{P}\right)×\left(\frac{ΔP}{Q}\right)$

$\left(\frac{ΔQ}{Q}\right)×\left(\frac{P}{ΔP}\right)$

The correct answer is option (3) : $\left(\frac{ΔQ}{Q}\right)×\left(\frac{P}{ΔP}\right)$