Mental math tricks

Some children might be delighted to learn math 'tricks' - curious ways to do calculations such as multiplying 2-digit numbers.

The 'tricks' do not contain any magic but are based on solid mathematical principles.

For example, to subtract any number from 1000 or 10,000 or any power of ten... just subtract from 999 or 9999 etc. and add 1.

Subtracting 10,000 - 2,596 with the usual method in columns, you will get into lots of borrowing over zeros... and end up having a row of nines to subtract from - except in the ones column where you have 10.

So 10,000 - 2,596 is quickly done by looking at each digit's difference to 9 - except in the case of one's digit, when you will subtract from 10. The result: 7,404.



Another 'trick' is called vertically and crosswise and applies to multiplication.

It can easily be proven to work using simple algebra. But it is a nice little mental math method that can impress kids.

Read more about that trick here. You can also practice online.

(Please note: this so-called 'vedic' math probably is NOT from Indian vedas or anything. The original author of the book with that name just claimed that but it seems his claims have no base. It's just a system of mental math calculations. Learning a few tricks like that can be just some simple fun.)

Comments

Hi!
Nice article on vedic maths!
I would like to point you to my blog http//vedicmathsindia.blogspot.com on the subject.
This has some amazing slide shows to benefit from.

Do check it out and give me a feedbck.

Wishes
Gaurav
Joe Wood said…
Interesting "tricks"! As a former mathematics teacher in the public schools and a future teacher in the public schools, these will be nice things to pass on to my students. My students always found math more enjoyable if they had some little trick to use, such as using thier hands to multiply by nine.

JW
Anonymous said…
Another site to examine is the "Tricks" section in http://www.pedagonet.com

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