The following fun math may seem like a joke, but it is real.
Check it using your calculator!

1 x 9 + 2                  = 11
12 x 9 + 3                = 111
123 x 9 + 4              = 1111
1234 x 9 + 5            = 11111
12345 x 9 + 6          = 111111
123456 x 9 + 7        = 1111111
1234567 x 9 + 8      = 11111111
12345678 x 9 + 9    = 111111111
123456789 x 9 +10 = 1111111111

9                 = 1 + 8 x 1
98               = 2 + 8 x 12
987             = 3 + 8 x 123
9876           = 4 + 8 x 1234
98765         = 5 + 8 x 12345
987654       = 6 + 8 x 123456
9876543     = 7 + 8 x 1234567
98765432   = 8 + 8 x 12345678
987654321 = 9 + 8 x 123456789


1 x 8 + 1                 = 9
12 x 8 + 2               = 98
123 x 8 + 3             = 987
1234 x 8 + 4           = 9876
12345 x 8 + 5         = 98765
123456 x 8 + 6       = 987654
1234567 x 8 + 7     = 9876543
12345678 x 8 + 8   = 98765432
123456789 x 8 + 9 = 987654321

9 x 9 + 7               = 88
98 x 9 + 6             = 888
987 x 9 + 5           = 8888
9876 x 9 + 4         = 88888
98765 x 9 + 3       = 888888
987654 x 9 + 2     = 8888888
9876543 x 9 + 1   = 88888888
98765432 x 9 + 0 = 888888888

                1 x 1                = 1
              11 x 11              = 121
            111 x 111            = 12321
          1111 x 1111          = 1234321 
        11111 x 11111        = 123454321 
      111111 x 111111      = 12345654321
    1111111 x 1111111    = 1234567654321
  11111111 x 11111111  = 123456787654321
111111111 x 111111111=12345678987654321


Incredible, is it not? 111,111,111 x 111,111,111 = 12,345,678,987,654,321