# 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.