1. The area of a 7 inch pizza
A = pi r^2
We need the radius
r = d/2 = 7/2 = 3.5 inches
A = 3.14 ( 3.5)^2 = 38.465 in ^2 = 38.5 in^2
The area of a 11 inch pizza
A = pi r^2
We need the radius
r = d/2 = 11/2 = 5.5 inches
A = 3.14 ( 5.5)^2 = 94.985 in ^2 = 95.0 in^2
2. The total area of the pizzas is found by adding the areas together
2* 38.5+95.0 = 77+95=172 in ^2
3. 2 7 inches pizzas is 77 inches^2 while 11 inches pizza is 95 in^2 so you get more pizza with the 11 inch pizza
4. We can use ratios to determine the cost for 2 7 inch pizzas
95 inches ^2 77 inches ^2
---------------------- = --------------
9.99 cost
Using cross products
95 * cost = 9.99 *77
95 * cost = 769.23
cost = 769.23/95
cost = 8.10
The two pizzas should cost 8.10 to be the same value
5. Compare 1 7 inch pizza to 1 11inch pizza
95 inches^2 - 38.5 inches^2 = 56.5 inches ^2 difference
6. Take the area that is more ( 56.5) and divide by the area of the 7 inch to get the percent more
56.5 / 38.5 = 1.467532
Change to percent form
146.7532 %
7. Take the area of 1 7 inch pizza 38.5 inches ^2 and divide by 4
38.5 /4 =9.625 inches ^2
Multiply by 3 for 3 slices
3 * 9.625 =28.875 inches ^2
8. 5 slices of an 8 slice pizza is 5/8 = .625 = 62.5 %
Multiply .625 by the area of the pizza
.625 * 95 =59.375 inches ^2