6 Comparison Number Stories

Chapter six introduces a new kind of number story:  comparison.  Here are a few examples:

         Susan is 23 years old.  Tom is 11.  How many years younger is Tom than Susan?

         The bakery sold 35 peanut butter cookies and 58 chocolate chip cookies.  How many more chocolate chip cookies did it sell than peanut butter? 

         Joey scored 30 points.  Max scored 12 points.  How many more points did Joey score than Max?

In this chapter, the diagram box that the students use teaches them that they are looking for the difference, and that one strategy in solving the problem is to write it out as an addition equation.

In the story above about Joey and Max, the number model would be:

12  +  ?  = 30

We also talk about how writing it as a subtraction equation will help you solve it too:

30 – 12  =  ?

The main way to practice this at home is to make up story problems that are comparison number stories and then talk about how to use the numbers to come up with the answer.  Keep the numbers low and the stories short.  Here are some examples:

         Tim has 10 fish.  Lisa has 13 fish.  How many fewer does Tim have than Lisa?  

         Richard is eight.  Sarah is 11.  How much younger is Richard than Sarah?

         Lisa drove 20 miles.  Mark drove 9 miles.  How many more miles did Lisa drive than Mark?

         Box A weighs 31 pounds.  Box B weighs 46 pounds.  How much lighter is Box A than Box B?

It’s important for the students to tell some of these stories too.  It’s also good to remember to use fewer than and not always more than because the students get used to hearing more than so often that fewer than sometimes throws them off.

After the students are comfortable with this type of story.  You might mix it up by telling a non-comparison number story:

         There were 36 fish in the tank.  The pet store sold 20.  How many fish are in the tank now?

         The top shelf has 17 books on it.  The bottom shelf has 30.  How many books are there in all?