% change in quantity% change in priceElasticity of Demand========2600–2800(2600+2800)÷2× 100–2002700× 100–7.4180–70(80+70)÷2× 1001075× 10013.33–7.41%13.33%0.56

$$\begin{array}{rcl}\text{\% change in quantity}& =& \frac{2600–2800}{\left(2600+2800\right)÷2}\mathrm{\times \; 100}\\ & =& \frac{\mathrm{–200}}{2700}\mathrm{\times \; 100}\\ & =& \mathrm{–7.41}\\ \text{\% change in price}& =& \frac{80–70}{\left(80+70\right)÷2}\mathrm{\times \; 100}\\ & =& \frac{10}{75}\mathrm{\times \; 100}\\ & =& 13.33\\ \text{Elasticity of Demand}& =& \frac{\mathrm{–7.41\%}}{\mathrm{13.33\%}}\\ & =& 0.56\end{array}$$ 

% change in quantity% change in priceElasticity of Demand========2200–2400(2200+2400)÷2× 100–2002300× 100–8.7100–90(100+90)÷2× 1001095× 10010.53–8.7% 10.53%0.83

$$\begin{array}{rcl}\text{\% change in quantity}& =& \frac{2200–2400}{\left(2200+2400\right)÷2}\mathrm{\times \; 100}\\ & =& \frac{\mathrm{–200}}{2300}\mathrm{\times \; 100}\\ & =& \mathrm{–8.7}\\ \% \text{change in price}& =& \frac{100–90}{\left(100+90\right)÷2}\mathrm{\times \; 100}\\ & =& \frac{10}{95}\mathrm{\times \; 100}\\ & =& 10.53\\ \text{Elasticity of Demand}& =& \frac{\mathrm{–8.7\% }}{\mathrm{10.53\%}}\\ & =& 0.83\end{array}$$ 

% change in quantity% change in priceElasticity of Demand========1600–18001700× 100–2001700× 100–11.76130–120125× 10010125× 1008.00–11.76% 8.00%–1.47

$$\begin{array}{rcl}\text{\% change in quantity}& =& \frac{1600–1800}{1700}\mathrm{\times \; 100}\\ & =& \frac{\mathrm{–200}}{1700}\mathrm{\times \; 100}\\ & =& \mathrm{–11.76}\\ \text{\% change in price}& =& \frac{130–120}{125}\mathrm{\times \; 100}\\ & =& \frac{10}{125}\mathrm{\times \; 100}\\ & =& 8.00\\ \text{Elasticity of Demand}& =& \frac{\mathrm{–11.76\% }}{\mathrm{8.00\%}}\\ & =& \mathrm{–1.47}\end{array}$$ 

% change in quantity% change in priceElasticity of Supply========70–50(70+50)÷2× 1002060× 10033.33$9–$8($9+$8)÷2× 10018.5× 10011.7633.33%11.76%2.83

$$\begin{array}{rcl}\text{\% change in quantity}& =& \frac{70–50}{\left(70+50\right)÷2}\mathrm{\times \; 100}\\ & =& \frac{20}{60}\mathrm{\times \; 100}\\ & =& 33.33\\ \text{\% change in price}& =& \frac{\mathrm{\$9}–\mathrm{\$8}}{\left(\mathrm{\$9}+\mathrm{\$8}\right)÷2}\mathrm{\times \; 100}\\ & =& \frac{1}{8.5}\mathrm{\times \; 100}\\ & =& 11.76\\ \text{Elasticity of Supply}& =& \frac{\mathrm{33.33\%}}{\mathrm{11.76\%}}\\ & =& 2.83\end{array}$$ 

% change in quantity%change in priceElasticity of Demand========88–80(88+80)÷2× 100884× 1009.52$11–$10($11+$10)÷2× 100110.5× 1009.529.52%9.52%1.0

$$\begin{array}{rcl}\text{\% change in quantity}& =& \frac{88–80}{\left(88+80\right)÷2}\mathrm{\times \; 100}\\ & =& \frac{8}{84}\mathrm{\times \; 100}\\ & =& 9.52\\ \text{\%change in price}& =& \frac{\mathrm{\$11}–\mathrm{\$10}}{\left(\mathrm{\$11}+\mathrm{\$10}\right)÷2}\mathrm{\times \; 100}\\ & =& \frac{1}{10.5}\mathrm{\times \; 100}\\ & =& 9.52\\ \text{Elasticity of Demand}& =& \frac{\mathrm{9.52\%}}{\mathrm{9.52\%}}\\ & =& 1.0\end{array}$$ 

% change in quantity% change in priceElasticity of Supply========100–95(100+95)÷2×100597.5×1005.13$13–$12($13+$12)÷2× 100112.5× 1008.05.13%8.0%  0.64

$$\begin{array}{rcl}\text{\% change in quantity}& =& \frac{100–95}{\left(100+95\right)÷2}\times 100\\ & =& \frac{5}{97.5}\times 100\\ & =& 5.13\\ \text{\% change in price}& =& \frac{\mathrm{\$13}–\mathrm{\$12}}{\left(\mathrm{\$13}+\mathrm{\$12}\right)÷2}\mathrm{\times \; 100}\\ & =& \frac{1}{12.5}\mathrm{\times \; 100}\\ & =& 8.0\\ \text{Elasticity of Supply}& =& \frac{\mathrm{5.13\%}}{\mathrm{8.0\% }}\\ & =& 0.64\end{array}$$ 

Percentage change in  quantity demandedPercentage change in income========[(change in quantity)/(original quantity)] × 100[22 – 30]/[(22 + 30)/2] × 100–8/26 × 100–30.77[(change in income)/(original income)] × 100[38,000 – 25,000]/[(38,000 + 25,000)/2] × 10013/31.5 × 10041.27

$$\begin{array}{rcl}\text{Percentage change in quantity demanded}& =& \text{[(change in quantity)/(original quantity)] × 100}\\ & =& \text{[22 – 30]/[(22 + 30)/2] × 100}\\ & =& \text{–8/26 × 100}\\ & =& \text{–30.77}\\ \text{Percentage change in income}& =& \text{[(change in income)/(original income)] × 100}\\ & =& \text{[38,000 – 25,000]/[(38,000 + 25,000)/2] × 100}\\ & =& \text{13/31.5 × 100}\\ & =& \text{41.27}\end{array}$$