An alternative subtraction algorithm Trade-First Subtraction An alternative subtraction algorithm

12 When subtracting using this algorithm, start by going from right to left. 8 12 2 9 3 2 - 3 5 6 Ask yourself, “Is the top number bigger in the one’s column?” In this problem the 2 on top is smaller than the 6 on bottom. So I need to regroup, by borrowing from the ten’s column. I can only borrow from ONE place to the left. 5 7 6 Move to the tens column. I cannot subtract 5 from 2, so I need to regroup by borrowing from the hundreds column. In the hundreds column, 8- 3 does not need regrouping. Now subtract column by column right to left

2 2 7 7 2 5 - 4 9 8 11 Let’s try another one together 15 1 6 15 1 7 2 5 - 4 9 8 Ask yourself, “Is the top number bigger in the one’s column?” In this problem the 5 on top is smaller than the 8 on bottom. So I need to regroup, by borrowing from the ten’s column. 2 2 7 Move to the tens column. I cannot subtract 9 from 1, so I need to regroup. In the hundreds column, 6-4 does not need regrouping. Now subtract column by column right to left

6 5 5 9 4 2 - 2 8 7 Let's see if you're right. Congratulations! 13 12 9 4 2 - 2 8 7 Now, do this one on your own. 6 5 5 Let's see if you're right. Congratulations!

Last one! This one is tricky! 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!