Learn how to quickly multiply two numbers from 11 to 19 in your head.
With this trick, you will be able to multiply any two numbers from 11 to 19 in your head quickly, without the use of a calculator.
I will assume that you know your multiplication table reasonably well up to 10x10.
Lets try 15 x 13.
1. Always place the larger number of the two on top in your mind.
2. Now add 15 + 3 = 18
3. Add a zero behind it (i.e., multiply by 10) to get 180.
4. Multiply the unit digit in this case (3 x 5 = 15)
5. Add the answers from steps 3 and 4 to get your answer. 180 + 15 = 195.
That''s it! Wasn''t that easy? Practice it on paper first!