The Magic of number 9

When you multiply any number by nine the digit of the answer will add up to nine.

A few examples will make this clear:

9 x 3 = 27   (2+7 = 9)

9 X 9 = 81   (8+1 = 9)

11 X 9 = 99 (9 +9 = 18) ( 1+8 = 9)

Now, how about digits of a number that add up to 9?

144 (1+4+4 = 9)

Let’s try :

 144 X 12345 = 1777680

1+7+7+7+6+8+0 = 36 (3+6 = 9)

Take a few numbers at random and try them yourself.

How does this help us in checking answers?

If any of the numbers you multiply with is a nine or the digits add up to nine, the answer

when reduced to a single digit must be nine.

So to check the answer of say,

1233 X 53 X 467 = 30517983

Here, for checking your answer after having worked out the first time is to just add up the digits of the answer because one of the numbers (1233) you had used to multiply adds up to 9.

So, adding the digits of the answer: 3+0+5+1+7+9+8+3 = 36 (3+6= 9)

We’ll use this to check out answers even faster in our next article.

Until then, have fun with playing around with the number 9