so 209 is the first number with the appropriate 2:1 ratio (edited).
so 209 is the first number with the appropriate 2:1 ratio (edited).
For small values of X < 10
11X = X+X, 2X always even
For slightly larger values of X, where 11X < 200
11x10 = 110, (starts out even)
11x11 = 121, (both of the first two digits increment by one, flipping even or odd ... in unison)
11x18 = 198, (only two signs will flip until we increment the 100s place, when that happens we will reverse three signs instead of two)
11x19 = 209, (now, three instead of two flip, and our sum comes up odd for the first time, 2+0+9=11)
1+6+9+4=20 so that's not it either.
By checking manually, it's 209.
19x11=209 2+0+9=11
The way you are doing doesn't seem correct even if what you said it's true, you aren't multiplying by 11.
I have no idea what the reasoning to prove the negative would be. I'd be interested to read it, if anyone knows.