Guided Math, math

#mathematizethis: fractions

Wednesday is pizza day at our school.  As I prepared to hand pizza out to my student, a little voice whispered: “#mathematizethis!”  So of course I took a picture before passing it around.  (To clarify, taking pictures of food is not a thing I usually do!)

Just for good measure, I took this picture too, and I was glad for it.

Today, Thursday, I used these pictures for a Number Talk.  I put up the pizza picture and said, “What do you see?”

Answers included:


  • There are 2 pieces of pizza missing.  (This might not seem like a big deal, but it showed me that they could extrapolate the information by comparing the 2 pizzas.  This came about as people said, “There is one whole pizza and one part of a pizza.”  And “There are 10 pieces in a whole pizza.” And “I can see 5 cheese, and 3 ham, so two must be missing because we need 10 for a whole pizza.”
  • At first, they were all about the counting.  (We have done only 1 other fraction Number Talk.) One girl said “I saw 1,2,3,4,5 on one half, so that means 5 on the other half, then 5 on the other half, so that’s 15.  Then 3 more, so there are 18 pieces of pizza.” UNITIZING!!!  AND SUBITIZING!!!
  • Soon after that, the fractions started rolling in.
    • 3/18 are ham
    • 15/18 are cheese
    • 2/18 are missing. (We talked about how it was really 2/20 missing.)
  • I asked, “What fraction of the pizza would a person have if they only had 1 piece?”  I  am super excited that 1 person said 1/10 since we’d established that 10/10 is a whole pizza.  Nobody argued for 1/18, and nobody looked confused, so I call that a win.


  • There is one milk missing.  9 can fit in the box.
  • 1/8 of the milk are plain.  7/8 are chocolate. They went to fractions much quicker the second time.

I asked what they would do if a class ordered more than 9 milks.  Most agreed you could stack the milk on top, but some thought a second box would be required.

Overall, I am super-nerdy excited about how this went.  It’s a contextualized problem, and one that they will encounter again because pizza comes every week.  I am also thinking this could be a Guided Math centre question at the beginning of every month.  The number of children who order pizza tends to change a bit every month.  AND, we could take pictures of the pizza in other classes.

I am going to teach fractions earlier next year just so I can do this!  And then I am going to teach graphing so we can graph our results. I just decided that right now, so if you don’t see this reflected in my long range plans, please hold me to it!