



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 
