When we add 1,000 to a four-digit number, we must increase the digit in the thousands column by 1.
Here is the number 1,623 shown on an abacus.
Notice how the abacus says units. Units are another word for ones.
When we add 1,000 we add an extra number to the thousands column.
1,623 + 1,000 = 2,623
Example
Add 1,000 to:
5,028
Answer
We increase the 5 in the thousands column by 1 to get 6 in that column.
5,028 + 1,000 = 6,028
When we subtract 1,000 from a four-digit number, we must decrease the digit in the thousands column by 1.
Here is the number 4,705 shown on an abacus.
When we subtract 1,000 from it, we take away one number from the thousands column.
4,705 - 1,000 = 3,705
Example 1
Subtract 1,000 from:
5,097
Answer
We decrease the 5 in the thousands column by 1 to get 4 in that column.
5,097 - 1,000 = 4,097
Example 2
Subtract 1,000 from:
1,060
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.
1,060 - 1,000 = 0060 = 60
Does that make sense?
Let's practise this in the questions that follow.