3-Digit Subtraction & Across Zeros

Practise subtracting three-digit numbers with borrowing — including the tricky case of borrowing across zeros.

Grade 3 · 3.NBT⚡ Place-value fluency
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How to subtract three-digit numbers

Three-digit subtraction uses the same borrowing method as two-digit, with one extra column. The hard case is borrowing across a zero: when the column you want to borrow from is 0, you have to borrow from further along first.

  1. Work right to left, borrowing whenever the top digit is too small.
  2. If you need to borrow from a 0, borrow from the next column first — that turns the 0 into a 10, then it can give 1 to its right.
  3. Subtract each column once the borrowing is sorted.

Worked examples

Borrowing once256 − 178 — ones: borrow for 16 − 8 = 8; tens: 4 − 7 borrow → 14 − 7 = 7; hundreds: 1 − 1 = 0. Answer: 78.
Across a zero503 − 167 — the tens digit is 0, so borrow from the hundreds first: 503 becomes 4 hundreds, 9 tens, 13 ones. Then 13−7 = 6, 9−6 = 3, 4−1 = 3. Answer: 336.
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Tips & common mistakes

Across-zero borrowing is where most errors live — take it slowly and rewrite the digits as you regroup. An estimate is your safety net: 503 − 167 is about 500 − 170 = 330, close to 336.

  • Getting stuck at a 0 — remember you borrow from the next non-zero column, which cascades back.
  • Forgetting to reduce a digit after it lends a ten.
  • Columns drifting out of alignment with bigger numbers.

Frequently asked questions

What grade is 3-digit subtraction?

It is a grade 3 skill, extending the 2-digit borrowing method by one column.

What does “borrowing across zeros” mean?

When the column you want to borrow from is 0, it has nothing to give, so you borrow from the next column along first — the borrow cascades.

Why is subtracting across zeros so tricky?

Because one borrow triggers another. Writing out the regrouped digits (turning 503 into 4, 9, 13) makes it manageable.

How can we check the answer?

Add the answer to the number you subtracted; it should give back the number you started with.

Any tip for the alignment?

Lined paper turned sideways, or graph paper, keeps the hundreds, tens and ones in their own columns.

Keep practising

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