Subtraction with Regrouping

🎯 What Will We Learn Today?

What if the top digit is smaller than the bottom digit in subtraction? That's when we borrow from the next column — also called regrouping! Today we'll master this crucial skill.

📚 What Is Borrowing (Regrouping)?

Borrowing happens when you can't subtract a bigger digit from a smaller one. You "borrow" 1 from the next column, turning it into 10 in the current column:

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5¹2 (52 = 5 tens + 2 ones → borrow 1 ten = 4 tens + 12 ones)

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25
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Can't do 2 − 7? Borrow 1 ten → 12 − 7 = 5. Then 4 − 2 = 2. Answer: 25.

🎮 Step-by-Step Borrowing

Example 1: 73 − 48

Step 1 — Ones: 3 − 8? Can't do it! Borrow 1 from the tens.
73 becomes 6 tens + 13 ones. 13 − 8 = 5.

Step 2 — Tens: 6 − 4 = 2.

Answer: 25

Example 2: 324 − 156

Ones: 4 − 6? Borrow → 14 − 6 = 8
Tens: 1（after borrowing）− 5? Borrow from hundreds → 11 − 5 = 6
Hundreds: 2 − 1 = 1

Answer: 168

💡 Borrowing Across Zero

When you need to borrow from a zero, keep going left until you find a non-zero digit!

500 − 234:
0 − 4? Borrow → 50 becomes 49, ones becomes 10. 10 − 4 = 6
9 − 3 = 6, 4 − 2 = 2
Answer: 266