Multiplying three digit number by 10001

The product of a 2-digit number and 10,001 + 21 is:

1. the two digits,
2. two zeros,
3. the two digits,
4. add 21.

Example:
29 × 10001 + 21

1. 29 × 10001 = 290029
2. 290029 + 21 = 290050

Multiplying a 3-digit number by 10001 and adding 201

The product of a 3-digit number and 10,001 + 201 is:

1. the three digits,
2. one zero,
3. the three digits,
4. add 201.

Example:
436 × 10001 + 201

1. 437 × 10001 = 4370437
2. 4370437 + 201 = 4370638

Multiplying a 4-digit number by 10001 and adding 2001

The product of a 4-digit number and 10,001 + 2001 is:

1. the four digits, repeated once
2. add 2001.

Example:
6741 × 10001 + 2001

1. 6741 × 10001 = 67416741
2. 67416741 + 2001 = 67418742