1. A Subtraction Algorithm

2. Trade First “The Trade First algorithm resembles the traditional method of subtraction, except that all the trading is done before all the subtraction, allowing the user to concentrate on one thing at a time.” “The Trade First algorithm resembles the traditional method of subtraction, except that all the trading is done before all the subtraction, allowing the user to concentrate on one thing at a time.” This is an easy to learn method that is very efficient. Vertical lines can be used to help the students focus on one column at a time and reduce mistakes. Based on EM resources

3. When subtracting using this algorithm, start by going from left to right. Ask yourself, “Do I have enough to subtract the bottom number from the top in the hundreds column?” In this problem, 9 - 3 does not require regrouping. Move to the tens column. I cannot subtract 5 from 3, so I need to regroup. Move to the ones column. I cannot subtract 6 from 2, so I need to regroup. Now subtract column by column in any order 9 3 2 - 3 5 6 8 13 12 2 7 6

4. When subtracting using this algorithm, start by going from left to right. Ask yourself, “Do I have enough to subtract the bottom number from the top in the hundreds column?” In this problem, 7 - 4 does not require regrouping. Move to the tens column. I cannot subtract 9 from 2, so I need to regroup. Move to the ones column. I cannot subtract 8 from 5, so I need to regroup. Now subtract column by column in any order 7 2 5 - 4 9 8 6 12 11 15 2 2 7

5. 9 4 2 - 2 8 7 8 14 13 12 6 5 5