What is the best way to study mental arithmetic?

## Answer

Dear Jane,

Practice makes perfect ! I practice all the time, first with small numbers, which I can do well and then more and more difficult 3 x 4, 11 x 11, 12 x 13, … If I have to do something annoying, and that takes one minute, I think after: how many minutes are there in an hour, how many hours in a day, so how many minutes in a day? Are there any fun things left to do? Then I usually don’t mind doing something stupid anymore. Sometimes I think even further, how many days do I have in my life, how many hours, how many minutes.

There are also many tricks that you can discover if you pay close attention.

For example: 3 x 4 = 4 x 3, 2 x 13 = 13 x 2, etc.

Furthermore, you also have that 5 x 36 = 5 x (6 x 6) = 5 x ((2 x 3) x 6) = 5 x 2 x 3 x 6 = 10 x 3 x 6 = 10 x 18 = 180.

By using this, you can sometimes come to a result faster.

Another trickier trick: 3 x 23 the previous trick doesn’t work here, you can do the following: 3 x 23 = 3 x (20 + 3) = (3 x 20) + (3 x 3) = 60 + 9 = 69

Can you understand why the tricks work?

You can write exercises for yourself on a sheet of paper, and then solve them and check them with a calculator or a calculator on the computer.

Good luck !

More websites here

http://www.hetspoorbasisschool.be/ICT/weblinks5deleerjaar.htm#Hoofdreken

http://users.telenet.be/kabaja/web exercises/hoofdreken.htm

## Answered by

#### ir. bruno Bauwens

Computer Sciences

http://www.ugent.be

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