Subtraction with carrying - The new method
A lot has changed since we went to school. Children are very quick to point out when parents are doing something wrong, it is a great sign that they understand what they are meant to do. So how does the new subtraction work?
Traditionally when carrying we used to borrow from the number underneath. When you think about the logic, this is incorrect because what we are really doing is borrowing from the column beside the number. For example:
722 -
118
To make this work we borrow one lot of ten from the tens column on the top row. Our number goes from 722 to 710 + 12 (still 722). We can subtract 8 from 12 leaving 4. The rest of this problem requires no more trading.
For more information please see the subtraction rap below.
Traditionally when carrying we used to borrow from the number underneath. When you think about the logic, this is incorrect because what we are really doing is borrowing from the column beside the number. For example:
722 -
118
To make this work we borrow one lot of ten from the tens column on the top row. Our number goes from 722 to 710 + 12 (still 722). We can subtract 8 from 12 leaving 4. The rest of this problem requires no more trading.
For more information please see the subtraction rap below.