Tutorial 87
Squaring special numbers (9's and final 5)
  1. Choose a number with repeating 9's and a final 5.
  2. The square is made up of:
    • same number of 9's as there are repeating 9's
    • same number of 0's
    • a final 25

   Example:

  1. If the number to be squared is 9995:
  2. The square has:

    same number of 9's as
       repeating 9's:         9 9 9
    same number of 0's as 9's
       in the square               0 0 0
    a final 25                           2 5

  3. So 9995 × 9995 = 99900025.

   See the pattern?

  1. If the number to be squared is 999995:
  2. The square has:

    same number of 9's as
       repeating 9's:        9 9 9 9
    same number of 0's as 9's
       in the square                0 0 0 0
    a final 25                              2 5

  3. So 999995 × 999995 = 999990000025.