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.