Multiplying a 2-digit number by 1001
              and adding 21

1. Select a 2-digit number.
2. Write it twice.
3. Write one zero between the 2-digit numbers.
4. Add 21.

   Example:

   1. 12 x 1001 = 12012
      12012 + 21 = 12033
   2. So 12 x 1001 + 21 = 12033

   Multiplying a 3-digit number by 1001
              and adding 201

1. Select a 3-digit number.
2. Write it twice.
3. Add 201.

   Example:

   1. 123 x 1001 = 123123
   2. 123123 + 201 = 123324
   3. So 123 x 1001 + 201 = 123324

Create variations by changing the number to be added or by giving a number to be subtracted. In either case, make the number an easy one to handle mentally