160112

When you pick a number between 1-10, for an example you could choose 2 and then you would add 9 and then add them together it will equal 11 and then you would add 1 and 1 together you will get your original number. Here are the examples 1+9=10 and 1+0=1, 2+9=11 and 1+1=2, 3+9=12 and 1+2=3, 4+9=13 and 1+3=4, 5+9=14 and 1+4=5, 6+9=15 and 1+5=6, 7+9=16 and 1+6=7, 8+9=17 and 1+7=8, 9+9=18 and 1+8=9, 10+9=19 and 1+9=10. This works because whenever you add by 9 it is always one less than the number you were adding to so if you were adding something like 6 to 9 it would equal 15 and the 5 is 1 less than the 6 and if you add 1 it would go back to the original number [6]. Furthermore, you can use numbers 1-10 and some higher numbers to multiply. For example 1x9=9 and 0+9=9, 2x9=18 and 1+8=9, 3x9=27 and 2+7=9, 4x9=36 and 3+6=9, 5x9=45 and 4+5=9, 6x9=54 and 5+4=9, 7x9=63 and 6+3=9, 8x9=72 and 7+2=9, 9x9=81 and 8+1=9, 9x10=90 and 9+0=9, 9x12=108 and 1+0+8=9 and as you can see there is no 11 because it doesn't work and of course there are more possible solutions and you can see it works because all of them add up to 9.