Shortcuts - Easy Subtraction

Eva was 8 years and 7 months when this video was made.

The Problem

Suppose that you had 23 snakes and 5 of them slithered away. How many would you have left?

What To Look For In This Video

Instead of taking 5 from 23 Eva first takes 3 and then takes 2. As far as I know, no one has ever taught Eva to solve problems in this way, or even suggested as much. It is because
- she understands what the word problem means, and
- she has the ability to reason logically,
that she is able to use techniques like this.
It is interesting that Eva starts by explaining that this is the way that she would solve the problem. It seems to me that she understands that there are lots of ways in which it might be solved.
My only role here was to pose the problem and correct a very unimportant mistake.

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