Math Tricks

By admin

 

Fast way to square numbers ending in 5

Quick Square:

If you need to square a 2 digit number ending in 5,  you can do so very easily with this trick.  Multiply the first digit by itself + 1, and put 25 on the end. That is all!
252 = (2x(2+1)) & 25
2 x 3 = 6
625

The secret of the number 9 (Multiplying by 9)

The fast way to multiply by 11

 
We all know the trick when multiplying by ten – add 0 to the end of the number, but did you know there is an equally easy trick for multiplying a two digit number by 11? This is it:
Take the original number and imagine a space between the two digits (in this example we will use 26:
2_6
Now add the two numbers together and put them in the middle:
2_(2+6)_6
That is it – you have the answer: 286
If the numbers in the middle add up to a 2 digit number, just insert the second number and add 1 to the first:
9_(9+9)_9
(9+1)_8_9
10_8_9
1089 – It works every time.
Practice it on paper and there you go – amazing your friends!