--- title: "Adding and subtracting two two-digit numbers" description: "Add and subtract two two-digit numbers using concrete objects, pictorial representations, and mental methods" canonical: https://lightmysky.com/learn/mathematics/adding-and-subtracting-two-two-digit-numbers-mt_UQnAFPs83F source: https://lightmysky.com/learn/mathematics/adding-and-subtracting-two-two-digit-numbers-mt_UQnAFPs83F.md retrieved: 2026-09-12 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Adding and subtracting two two-digit numbers Add and subtract two two-digit numbers using concrete objects, pictorial representations, and mental methods Subject: Mathematics · Area: Addition & Subtraction · Ages 6 to 7 Page: https://lightmysky.com/learn/mathematics/adding-and-subtracting-two-two-digit-numbers-mt_UQnAFPs83F ## Ready when they can - Calculate 34 + 27 using base-ten blocks or column addition - Calculate 63 − 28 using a number line or partitioning - Explain a strategy for adding or subtracting two two-digit numbers ## Lesson: Adding two two-digit numbers You already know how to add tens in your head, like 30 + 20 = 50. Now you will add two two-digit numbers, like 34 + 27. Split each number into tens and ones. Add the tens together, then add the ones together. If the ones add up to ten or more, turn ten of them into one more ten. *(drawing: Start at 34. Hop 20 to land on 54. Hop 7 more to land on 61.)* **Example.** Leo adds 48 + 25. Tens: 40 + 20 = 60. Ones: 8 + 5 = 13. That is 1 ten and 3 ones, so he adds the extra ten to 60. 60 + 13 = 73. **Example.** Ava works out 63 − 28. Start at 63. Hop back 20 to land on 43. Hop back 8 more to land on 35. So 63 − 28 = 35. **Tip.** After you add, check the ones digit first. If the ones made ten or more, make sure you moved that extra ten over. Forgetting it is the easiest mistake to make. **Recap.** Add or subtract the tens, then the ones, and regroup an extra ten when the ones spill over. ## Practice 17 questions on this page, each with its working shown. ## Needs first - [Mental addition and subtraction (age 6+)](https://lightmysky.com/learn/mathematics/mental-addition-and-subtraction-age-6-mt_AKAtWEwpcj) - [Adding and subtracting tens mentally](https://lightmysky.com/learn/mathematics/adding-and-subtracting-tens-mentally-mt_I5j1ZWo2cn) ## Opens up - [Mental and written addition and subtraction](https://lightmysky.com/learn/mathematics/mental-and-written-addition-and-subtraction-mt_wzAZ8qFDc4)