How to calculate that #9 remains 9

How to calculate that #9 remains 9. It's Simple Multiplication and Addition, And It's Interesting.

Instructions

Difficulty: Easy

Things You’ll Need:

• Calculator

1. If you Multiply #9 with.
   
   #1 i, e, 9 x 1 = 9
2. #2..... 9 x 2 = 18, 1+8=9
   #3..... 9 x 3 = 27, 2+7=9
   #4..... 9 x 4 = 36, 3+6=9
3. #5..... 9 x 5 = 45, 4+5=9
   #6..... 9 x 6 = 54, 5+4=9
   #7..... 9 x 7 = 63, 6+3=9
4. #8..... 9 x 8 = 72, 7+2=9
   #9..... 9 x 9 = 81, 8+1=9
   #10.... 9 x 10 = 90, 9+0=9
5. #11..... 9 x 11 = 99, 9+9=18, 1+8=9
   #12..... 9 x 12 = 108, 1+0+8=9
   #13..... 9 x 13 = 117, 1+1+7=9
6. #14..... 9 x 14 = 126, 1+2+6=9
   #15..... 9 x 15 = 135, 1+3+5=9
   #16..... 9 x 16 = 144, 1+4+4=9

Tips & Warnings

• Learn the Table of 9.
• Don't go too long.