1. Pizza,
Pizza!
By: Tracy Balow & Kristen Moorhouse

2. Which is the better buy? 12 inch 9 inch thin crust pizza
for
$10.99
9 inch
thin crust pizza
for
$7.99

3. To solve this problem, which concept will you need to use?
a) the circumference of a circle OR
b) the area of a circle
Think, pair, share…

4. Try again! Circumference refers to the distance around a circle.
You would use circumference if you only wanted to eat the crust.
Click on the pizza to continue.

5. Correct! Area refers to the region contained by the whole pizza.
You would use area to find out how much pizza there is!

6. Now… can you write the formula to find the area of a circle?
Think, pair, share…

7. Now, find the area of each pizza. Round to the nearest hundredth.
A = in2
9” pizza
A = πr2
A = 3.14(4.5)2
A = 3.14(20.25)
A = in2
Remember the radius is half the diameter!
Think, pair, share…

8. Now, how can we use that information to find the better buy?
Recall, to find the better buy, you need to find the price per one unit (the unit rate!).
Soooooo, take the price and divide it by the area of the pizza.
This will give you the price per square inch of pizza!
Do this for both pizzas so you can compare their unit prices.
Vs.
Think, pair, share…

9. Now, find the unit rate of each pizza. Round to the nearest hundredth.
$10.99
in2 =
= $0.10/in2
9” pizza
$7.99
63.59 in2 =
= $0.13/in2
Think, pair, share…
Vs.

10. So, after doing all that work and getting all those answers…
Which pizza is the better buy?
And….
Why? Explain.
Think, pair, share…

11. Let’s review…. How did we solve the problem? What were the steps?
What did the original question ask?
What vocabulary did we need to know?
What information did we need to know to solve the problem?
How did we solve the problem? What were the steps?
How can we check our answer?
What standards were addressed?

12. Finally….
How would you solve this same problem if the pizzas had different thicknesses? Explain.
How would you solve this same problem if the pizzas were square? Explain.
Think, pair, share…