Shortcuts - Easy Subtraction

Eva was 7 years and 8 months at the time that this video was made.

The Problem

Pretend that you had 3 candies and that Rose gave you some more. Then you had 8 candies altogether. How many candies did Rose give you.

(This problem is an Easy Subtraction problem. It can be represented by the equation 8 - 3 = . But it can also be represented by the equation 3 + = 8. Thought of in that way it is a problem in Algebra.)

What To Look For In This Video

• Eva immediately sets out 3 candies.
• Right from the beginning it is clear that she is thinking "how many candies do I need to add to these 3 in order to have 8 altogether (in other words, "3 plus what will make 8?")
• She guesses 3, but immediately realizes that that cannot be right because 3 + 3 is only 6. She realizes that she will need to add more.
• Eva's second guess is that 3 + 6 = 8, but realizes immediately that 3 + 6 = 9. She also recognizes that 9 is 1 too much.

Click here to see Rose 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 Eva's and some thoughts on how to teach children to solve them.