When we **add** 1000 to a 4-digit number, we must increase the digit in the Thousands column by 1.

Here is the number 1623 shown on a **Thousands Hundreds Tens Ones** abacus.

*Notice how the abacus says units. Units are another word for ones.

When we add 1000 we add an extra number to the Thousands column.

1623 + 1000 = 2623

**Example**

Add 1000 to:

5028

**Answer**

We increase the 5 in the Thousands column by 1 to get 6 in that column.

5028 + 1000 = 6028

When we **subtract** 1000 from a 4-digit number, we must decrease the digit in the Thousands column by 1.

Here is the number 4705 shown on a **Thousands Hundreds Tens Ones** abacus.

When we subtract 1000 from it, we take away one number from the Thousands column.

4705 - 1000 = 3705

**Example 1**

Subtract 1000 from:

5097

**Answer**

We decrease the 5 in the Thousands column by 1 to get 4 in that column.

5097 - 1000 = 4097

**Example 2**

Subtract 1000 from:

1060

**Answer**

We decrease the 1 in the Thousands column by 1 to get 0 in that column.

Remember to leave off any zeros on the left hand side of a number.

1060 - 1000 = 0060 = 60