Subtraction by Regrouping
(Also called "borrowing" or "trading")
Subtraction
To subtract numbers with more than one digit:
- Write the numbers: first one on top, second directly below it, lining up the columns.
- Subtract one column at a time, as shown (press the play button):
Smaller Number - Bigger Number
But what if a column has a smaller number on the top?
How do we do 2 − 5 ?
The Solution: Make the "2" larger by "regrouping" (press arrow button):
So with regrouping we trade 1 ten for 10 ones, and the total stays the same.
In 32:
- the "3" means 3 tens,
- the "2" means 2 ones,
So we:
- reduce the 3 by 1
- increase the 2 by 10
And we get:
- 2 tens,
- 12 ones
And here is how to do it with a pencil and paper:
We use this method whenever a column has a smaller number on top, as in this example:
Zero
If the top digit is 0, we can’t subtract from it directly.
But we can make a 0 into a 10 by regrouping it first! Then we regroup from the 10 (which becomes a 9) and continue on.
Note: If there is more than one zero, keep regrouping left. Each zero becomes 9 until we reach a non-zero digit.
Now, you can practice with these Subtraction Worksheets