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Mathematics Is Fun!

The magic multiplication

Date : 15/12/2020

Author Information

Joseph

Uploaded by : Joseph
Uploaded on : 15/12/2020
Subject : Maths

Lovers of quick trick, lend me your ears!

It was about 5 years ago. I was teaching my child who is now in the Secondary school the multiplication tables.

By chance, I discovered that anything multiplied by 11 merely doubles itself! E.g. 2x11 is 22 5x11 is 55 9x11 is 99 but when we got to 10 and above, the rule of doubling doesn't work.

10x11 is 110

11x11 is 121

12x11 is 132 and from these, I discovered that to multiply a two digit number with 11, merely separate the digits, add the two digits and insert the figure in the middle produces the answer. Wow!


For example, 13 multiplied by 11 will be resolved as follows:


Step 1: Write 1 and 3 with a space between them.

Step 2: add 1 and 3 to get 4

Step 3: insert the 4 between 1 and 3 to get 143!

Now try 14 multiplied by 11 and share the trick with your friend!

You can really have fun with mathematics and still come out with distinction.


Joseph, ACCA

15 December 2020


This resource was uploaded by: Joseph