# Modeling - Easy Subtraction

Rose was 5 years and 8 months at the time that this video was made.

**The Problem**

Suppose that you have 3 snakes and that someone gives you some more so
that you now have a total of 7 snakes. How many snakes were you given?

(This problem is an example of Easy Subtraction. It can be represented
by the equation 7 - 3 = □. But
it can also be represented by the equation 3 + □ = 7.
Thought of in that way it is a problem in Algebra.)

**What To Look For In This Video**

- Rose starts by representing the 3 snakes that she initially had. Perhaps she is thinking "3 snakes plus some more snakes equals 7 snakes."
- But she then puts those 3 "snakes" aside and counts out a separate collection 7 snakes. She is now thinking about this problem in a different way.
- To solve the problem Rose takes 3 snakes from her collection of 7. She must be thinking (correctly) that she can solve this problem by taking the 3 snakes that she started with from the 7 snakes that she ended with to find out how many she was given.

Click here to see Eva solve a problem just
like this one, but in a different way.

Click here.
to download (in PDF format, in a new window) a detailed discussion of
problems like Rose's and some thoughts on how to teach children to
solve them.