Answer:
a. The percentage change in pizza prices is -25.00%.
b. The percentage change in pizza prices is 5.88%.
c. The cross elasticity of demand for pizza and skateboards is -23.53%.
We follow these steps to arrive at the answer.
<h3>a. Percentage change in price of pizza</h3>
The percentage change in price of pizza using the midpoint formula is:
![percentage change in price = ({\frac{P_{2} - P_{1}}{Average price})*100](https://tex.z-dn.net/?f=percentage%20change%20in%20price%20%3D%20%28%7B%5Cfrac%7BP_%7B2%7D%20-%20P_%7B1%7D%7D%7BAverage%20price%7D%29%2A100)
![Average Price = \frac{P_{2} + P_{1}}{2}](https://tex.z-dn.net/?f=Average%20Price%20%3D%20%5Cfrac%7BP_%7B2%7D%20%2B%20P_%7B1%7D%7D%7B2%7D)
In this question, P₁ is $18 and P₂ is $14
Substituting the values in the formula above we get,
![Average Price = \frac{14 + 18}{2}](https://tex.z-dn.net/?f=Average%20Price%20%3D%20%5Cfrac%7B14%20%2B%2018%7D%7B2%7D)
![Average Price = \frac{32}{2}](https://tex.z-dn.net/?f=Average%20Price%20%3D%20%5Cfrac%7B32%7D%7B2%7D)
![Average Price = 16](https://tex.z-dn.net/?f=Average%20Price%20%3D%2016)
![percentage change in price = (\frac{14 - 18}{16})* 100](https://tex.z-dn.net/?f=percentage%20change%20in%20price%20%3D%20%28%5Cfrac%7B14%20-%2018%7D%7B16%7D%29%2A%20100)
![percentage change in price = (\frac{-4}{16}) * 100](https://tex.z-dn.net/?f=percentage%20change%20in%20price%20%3D%20%28%5Cfrac%7B-4%7D%7B16%7D%29%20%2A%20100)
%
<h3>b. Percentage change in quantity demanded of skateboards</h3>
The percentage change in quantity of skateboards using the midpoint formula is:
![percentage change in quantity = (\frac{Q_{2} - Q_{1}}{Average Quantity})*100](https://tex.z-dn.net/?f=percentage%20change%20in%20quantity%20%3D%20%28%5Cfrac%7BQ_%7B2%7D%20-%20Q_%7B1%7D%7D%7BAverage%20Quantity%7D%29%2A100)
In this question, Q₁ is 330 and Q₂ is 350
Substituting the values in the formula above we get,
![Average quantity = \frac{Q_{2} + Q_{1}}{2}](https://tex.z-dn.net/?f=Average%20quantity%20%3D%20%5Cfrac%7BQ_%7B2%7D%20%2B%20Q_%7B1%7D%7D%7B2%7D)
![Average quantity = \frac{350 + 330}{2}](https://tex.z-dn.net/?f=Average%20quantity%20%3D%20%5Cfrac%7B350%20%2B%20330%7D%7B2%7D)
![Average quantity = 340](https://tex.z-dn.net/?f=Average%20quantity%20%3D%20340)
![percentage change in quantity = (\frac{350 - 330}{340})*100](https://tex.z-dn.net/?f=percentage%20change%20in%20quantity%20%3D%20%28%5Cfrac%7B350%20-%20330%7D%7B340%7D%29%2A100)
![percentage change in quantity = (\frac{20}{340})*100](https://tex.z-dn.net/?f=percentage%20change%20in%20quantity%20%3D%20%28%5Cfrac%7B20%7D%7B340%7D%29%2A100)
%
<h3>c. Cross Elasticity of demand of skateboards and pizza</h3>
We calculate the cross elasticity of demand as follows:
![Cross Elasticity Demand = \frac{percentage change in quantity of skateboards}{percentage change in price of pizza}](https://tex.z-dn.net/?f=Cross%20Elasticity%20Demand%20%3D%20%5Cfrac%7Bpercentage%20change%20in%20quantity%20of%20skateboards%7D%7Bpercentage%20change%20in%20price%20of%20pizza%7D)
![Cross Elasticity Demand = \frac{0.058823529}{-0.25}](https://tex.z-dn.net/?f=Cross%20Elasticity%20Demand%20%3D%20%5Cfrac%7B0.058823529%7D%7B-0.25%7D)
![Cross Elasticity Demand = -0.235294118](https://tex.z-dn.net/?f=Cross%20Elasticity%20Demand%20%3D%20-0.235294118)
%