Quote Originally Posted by jstar View Post
NO

You still need to write it down (imagine it?) so then you can make a 'normal' multiplication as well. Come on, just take the 10x and add the 1x:

10 x 23 + 1 x 23

The same with 9 btw (10x - 1x)

Another issue for me is that by applying this tricks you have no idea anymore about the logic behind it (cf. Rubik's cube).

We have a saying in Dutch: teach someone something like a monkey (iets als een aapje aanleren). It means people just execute something without knowing and understanding the logic why. Sure, it can be fun and convenient but I had big issues once with a math teacher who also worked this way.
Hi,

Actually we do teach children the logic behind it. Our main purpose is to let children know that Math is not rocket science, but it's based on very simple logics. The most important thing is to let them understand why and how we can solve a problem.

For our example of multiplication by 11, the method we showed is always accompanied by an explanation why we can do it that way.

We tell children that any number multiplied by 11, is actually equal to the number multiplied by 10 plus the number itself.

So if 23 x 11, it's equal to 230 + 23.

Because of this fixed pattern, it lead to a simplification where placing zero and adding subsequent number works.

Again, at Math Monkey we also emphasize that there's no right way of solving a Math problem. There's many different ways and it's up to the children to decide which way they're most comfortable with.

Hope that our explanation could clear some of your doubts, if not we're more than happy to show more examples