Trade First Subtraction Method
This method is most commonly used in the United
States and most parents learned to subtract in a way
that is very similar to this method.
Before any subtracting can be done, you need to go
through and decide if any "trading" needs to take
place. To do this, you must begin in the ones place
and examine each place value to determine if the top
digit is smaller than the bottom digit. If it is, trading
must occur. If it isn't or is equal, no trading is
necessary. Next, move on to the tens place value
and so on.
1. Trade in the 1's place value column, if necessary.
2. Trade in the 10's place value column, if necessary.
3. Subtract each place value.