Using Calculus to Calculate Elasticities

Using Calculus to Calculate Elasticities [Q:] I understand the equations you have on your site regarding the change in quantity demanded and change in price to calculate the elasticity. How would I convert this equation into those types? I dont quite understand what this equation means. No other info was given. Demand is Qx 110 - 4Px. What is price (point) elasticity at $5? [A:]Elasticity is given by the formula: Elasticity (percentage change in Z) / (percentage change in Y) We saw how to calculate various elasticities when were given numerical examples. But how do we calculate an elasticity when were given a formula such as Z f(X)? Use Calculus to Find the Elasticity! Using some fairly basic calculus, we can show that (percentage change in Z) / (percentage change in Y) (dZ / dY)*(Y/Z) where dZ/dY is the partial derivative of Z with respect to Y. Thus we can calculate any elasticity through the formula: Elasticity of Z with respect to Y (dZ / dY)*(Y/Z) Well look at how to apply this to four different situations: Using Calculus To Calculate Price Elasticity of DemandUsing Calculus To Calculate Income Elasticity of DemandUsing Calculus To Calculate Cross-Price Elasticity of DemandUsing Calculus To Calculate Price Elasticity of Supply Next: Using Calculus To Calculate Price Elasticity of Demand