Lesson 3 of 12
➖ Subtraction with Regrouping
What You'll Learn
- How to subtract using borrowing (regrouping)
- What to do when the top digit is smaller than the bottom
- How to check subtraction using addition
When You Need to Borrow
Sometimes the digit you are subtracting from is smaller than the digit you are subtracting. That is when you borrow from the next column.
Example: 72 - 38
- Ones: 2 - 8. We can't do this! Borrow 1 ten from the tens column.
- Now ones = 12 - 8 = 4. Tens column is now 6 (was 7, gave 1 away).
- Tens: 6 - 3 = 3.
- Answer: 34
Check Your Work!
Always verify subtraction by adding your answer back: 34 + 38 = 72 ✓. If it equals the original number, your subtraction is correct!
Subtracting Across Zero
Numbers with zeros in the middle (like 305 - 148) require borrowing across two columns. Take it one column at a time — borrow from the hundreds when the tens is 0.
305 - 148: borrow from hundreds to make tens = 10, then borrow from tens for ones. Work carefully column by column.
Quick Check
1. 72 - 38 = ?
2. How do you check that a subtraction answer is correct?
3. What do you do when the top digit in a column is smaller?