Multiplication involving series of 1's and equal no of digits in multiplicand & multiplier

Multiplication involving series of 1's and equal no of digits in multiplicand & multiplier is very easy to do.
For example.
      11
      11
----------
     121
--------

    11111
    11111
------------
123454321
------------

Its very simple. Count number of digits in multiplicand or multiplier. Then start from natural number 1 in ascending order till the digit count. After that start descending order till number 1.