Many students struggle to understand and remember the standard dynamic subtraction algorithm. Above is a great alternative to the standard algorithm. An alternative that brings understanding to what is being done when subtracting one number from another number. And it is easy to introduce. First play around with have and owe. Check out Crewton Ramone’s House of Math intro to negative numbers and integer toss game videos to see how to do this. From there you can quickly and easily introduce dynamic subtraction as shown above to even the littlest of kids. Start with smaller numbers first and then go bigger – after all bigger is funner! Don’t forget to use your blocks with all of this – keep it fun. After only a couple of examples you will find most children will be able to do dynamic subtraction with understanding.
Note: The minuend is the have and the subtrahend is the owe.
Thus: 15-8 would be have 15 owe 8 which can be further broken down to have 10 owe 0 and have 5 owe 8. 23-17 would be have 23 owe 17 which again can be further broken down to have 20 owe 10 and have 3 owe 7.
Also: With this method it doesn’t matter which place value you subtract first.