1. An alternative subtraction algorithm
Trade-First Subtraction
An alternative subtraction algorithm
Created by Rina Iati, South Western School District, Hanover, PA

2. Created by Rina Iati, South Western School District, Hanover, PA12
When subtracting using this algorithm, start by going from left to right. 8 12 13
Ask yourself, “Do I have enough to subtract the bottom number from the top in the hundreds column?” In this problem, 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

3. Created by Rina Iati, South Western School District, Hanover, PA11
Let’s try another one together 6 15 12
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

4. Created by Rina Iati, South Western School District, Hanover, PA13 8 12 14
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

5. Created by Rina Iati, South Western School District, Hanover, PA9
Last one! This one is tricky! 6 13 10 2 3 4
Let's see if you're right.
Congratulations!
Created by Rina Iati, South Western School District, Hanover, PA