Let's take an example of a 2-digit number for multiplying with 9.

79 X 9

Step 1:
Take the Unit digit 9 & subtract 1 from it. You get 8

Step 2:
Take Tenth digit & add 1 to it . You get 8.

Step 3.
Now subtract 8(answer from step 2) from 79, you get 71 & Subtract 8 ( answer from step 1) from 9 and you get 1.Required result is 711

79 X 9
8 8
----------
71 1

Answer is 711

Let's take another example:

18962 X 9

Step 1:
Take Unit digit 2 and subtract 1 from 2 , we get 1. Take rest of the digits & add 1 to 1896 , we get 1897

Step 2:
Subtracting 1897 from 18962 , we get 17065 & subtracting 1 from 9, we get 8

Answer: 170658

Another quick way to find the multiplication of a given number by 9 is to multiply the given number by 10 & subtract the given number from the product.