Elasticity of Demand is given by the formula.

$\frac{Q}{\Delta Q} \times \frac{P}{\Delta P}$

$\frac{\Delta Q}{Q} \times \frac{P}{\Delta P}$

$\frac{\Delta P}{P} \times \frac{\Delta Q}{Q}$

$\frac{\Delta Q}{P} \times \frac{Q}{P}$