Subtraction by "Regrouping"

(Also called "borrowing" or "trading")

To subtract numbers with more than one digit:

  • write down the larger number first and the smaller number directly below it
    making sure to line up the columns!

  • then do subtractions one column at a time like this (press play button):

Smaller Number - Bigger Number

  subtract before borrow  

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" like this (press play button):

 
 

In 32:

  • the "3" means 3 tens,
  • the "2" means 2 units,

So we:

  • reduce the 3 by 1
  • increase the 2 by 10

We use this method whenever a column has a smaller number on top, as in this example:

Zero

But we can't regroup from zero ...

But we can make a "0" into a "10" by regrouping it first, them carry on normally, like this:

 

Now, you can practice with these Subtraction Worksheets