01 + 11 = 12
12 + 11 = 23
23 + 11 = 34
34 + 11 = 45
45 + 11 = 56
56 + 11 = 67
67 + 11 = 78
78 + 11 = 89
[The pattern stops here because if you add 11 to 89, you'll get 100]
Did you notice the padding zero I put for the number 1 on the top? That was so it would have 2 digits!
98 - 11 = 87
87 - 11 = 76
76 - 11 = 65
65 - 11 = 54
54 - 11 = 43
43 - 11 = 32
32 - 11 = 21
21 - 11 = 10
[The pattern stops here because if you subtract 11 from 10, you'll get -1]
There must be a 1 for each digit column when you add or subtract consecutive-digit numbers for this trick to work...
012 + 111 = 123
123 + 111 = 234
234 + 111 = 345
345 + 111 = 456
987 - 111 = 876
876 - 111 = 765
765 - 111 = 654
654 - 111 = 543
...Otherwise, something like this will happen!
345 + 101 = 446
12 - 11 = 01
23 - 11 = 12
34 - 11 = 23
45 - 11 = 34
56 - 11 = 45
67 - 11 = 56
78 - 11 = 67
89 - 11 = 78
[If you subtract 11 from 1, you'll get -10]
Subtracting instead of adding gives you the previous, smaller consecutive-digit number in the pattern! (If the greater/greatest digit is on the right!)
98 + 11 = 109
87 + 11 = 98
76 + 11 = 87
65 + 11 = 76
54 + 11 = 65
43 + 11 = 54
32 + 11 = 43
21 + 11 = 32
10 + 11 = 21
[Adding 11 to 98 gave us a 3-digit number!]
If you add instead of subtract with the greater/greatest digit on the left, you get the next, bigger consecutive-digit number in the pattern!
12345 + 11111 = 23456
12345 - 11111 = 01234
54321 + 11111 = 65432
54321 - 11111 = 43210
See how the digits "slide" thru the sums? Cool, isn't it?
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© Derek Cumberbatch