Pre Algebra Fractions
Math-Prof HOME Arithmetic Table of Contents Ask A Question PREV NEXT

Pizza Slices
Fractions

 
 Most pizza places cut pizza into 8 slices like this.
 

 

 
 Math people (who really like pizza) 
 wanted a way to talk about slices of pizza. 
 They thought up a way to write how many slices they have 
 and how many slices there are in the whole pizza all at once. 
 The tricky part is the line they used to keep the two numbers apart.
 

 
 Example:
 
 If a pizza is cut into 8 slices, and we have 3 slices, 
 how much of the whole pizza do we have?
 

 
 OK, Let's look at this another way.
 
 Example:
 
 Say we have one slice of pizza.
 

 
 and someone gives us two more.

 

 
 Could we write that as  an addition problem?

 Sure. 

 Do it the same way you write any addition problem. 
 Write one thing. 
 Write a plus sign. 
 Write the other thing.
 

 
 We know the answer to this one. 
 If you start with 1 slice of pizza and get 2 more 
 you have 3 all together. 
 The whole pizza still has 8 slices so all together 
 the problem looks like this:
 

 
 More Examples:
 
 Add 2 slices plus 3 slices from an 8 slice pizza
 

 
 Add 4 slices plus 2 slices from an 8 slice pizza.
 

 
 In order for these problems to work, 
 the pizza slices must come from pizzas 
 cut into the same number of slices. 
 
 On another page we'll talk about what to do 
 when the pizzas have different numbers of slices. 
 
 Try another one ...
 
 Example:
 
 Add 5 slices plus 3 slices from an 8 slice pizza.
 

 
 Look at that one again. 
 We ended up with 8 slices. 
 That means we have 1 whole pizza. 
 So:
 

 
 How about this ...
 
 Example:
 
 Say we have 3 slices of pizza. 
 Then we eat one. 
 That's like subtraction isn't it?
 Sure is!
 

 
 Pizzas don't always have 8 slices. 
 Some have 12 slices. 
 A slice from one of those pizzas would be:
 

 
 Say we had one wacky pizza that was cut into only 3 slices. 
 If we had one of those slices, we would have:
 
 

   copyright 2005 Bruce Kirkpatrick

Math-Prof HOME Arithmetic Table of Contents Ask A Question PREV NEXT