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Trade-First Subtraction. An alternative subtraction algorithm . 12. When subtracting using this algorithm, start by going from left to right. 8. 12. 13. 9 3 2 - 3 5 6.
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Trade-First Subtraction An alternative subtraction algorithm Created by Rina Iati, South Western School District, Hanover, PA
12 When subtracting using this algorithm, start by going from left to right. 8 12 13 9 3 2 - 3 5 6 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. 5 7 6 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 Created by Rina Iati, South Western School District, Hanover, PA
11 Let’s try another one together 6 15 12 7 2 5 - 4 9 8 Start by going left to right. Ask yourself, “Do I have enough to take away the bottom number?” In the hundreds column, 7- 4 does not need regrouping. 2 2 7 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 trade. Now subtract column by column in any order Created by Rina Iati, South Western School District, Hanover, PA
13 8 12 14 9 4 2 - 2 8 7 Now, do this one on your own. 6 5 5 Let's see if you're right. Congratulations! Created by Rina Iati, South Western School District, Hanover, PA
9 Last one! This one is tricky! 6 13 10 7 0 3 - 4 6 9 2 3 4 Let's see if you're right. Congratulations! Created by Rina Iati, South Western School District, Hanover, PA