Dino Sums

Home › Class 3 Maths › Add three-digit numbers

Add three-digit numbers for Class 3

Adding numbers to 1000 with exchanges, one worked example step by step, and 5 questions to try. No timer, no account.

What it means

To add two three-digit numbers, add the ones, then the tens, then the hundreds. When a place adds up to ten or more, exchange ten of that place for one of the next place and carry it over, just like carrying with two-digit numbers.

Worked example: 456 + 278

  1. 1Add the ones: 6 + 8 = 14. Write 4 in the ones place. Carry 1 ten.
  2. 2Add the tens: 5 + 7 = 12, plus the carried ten = 13. Write 3 in the tens place. Carry 1 hundred.
  3. 3Add the hundreds: 4 + 2 = 6, plus the carried hundred = 7.
  4. 47 hundreds, 3 tens and 4 ones.

Carried amounts sit above the next column. Answer row in orange.

So 456 + 278 = 734.

Practice 5 questions

Question 1 of 5

Printable worksheets

Prefer paper? These sheets print on A4 and each has an answer key on the last page.

Add three-digit numbers - Class 3
Free printable PDF, with an answer key for grown-ups.PDF

Keep practising with Sumi

Dino Sums is a free maths practice app for Classes 1-5. Short untimed sessions, help that shows each step, no ads, no account.

Open Dino Sums - free

Works in the browser. Android app coming soon.

More topics

Subtract three-digit numbers Money stories Addition with carrying (Class 2) All Class 3 topics

Dino Sums is a free preview of maths practice for Classes 1-5. It is not a full course or a test.