--- title: "Place value understanding and number facts" description: "Use place value understanding and number facts to solve problems" canonical: https://lightmysky.com/learn/mathematics/place-value-understanding-and-number-facts-mt_kJGCjnuelW source: https://lightmysky.com/learn/mathematics/place-value-understanding-and-number-facts-mt_kJGCjnuelW.md retrieved: 2026-10-19 --- > **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`. # Place value understanding and number facts Use place value understanding and number facts to solve problems Subject: Mathematics · Area: Number Representation & Place Value · Ages 6 to 7 Page: https://lightmysky.com/learn/mathematics/place-value-understanding-and-number-facts-mt_kJGCjnuelW ## Ready when they can - Use knowledge that 34 = 30 + 4 to help add 34 + 20 = 54 - Solve 'I think of a number, add 10, and get 45. What was my number?' - Apply partitioning to solve a problem in an unfamiliar context ## Lesson: Using place value to add fast A two-digit number is made of tens and ones. The number 34 is 3 tens and 4 ones, or 30 + 4. Once you see a number this way, adding gets much faster. *(drawing: Start at 34 and hop forward 20. You land on 54, because 30 + 20 = 50 and the 4 ones stay put.)* **Example.** Zoe thinks of a number, adds 10, and gets 45. She knows 45 is 40 + 5. Adding 10 only changes the tens, so her starting number must have been 35, because 35 + 10 = 45. **Tip.** When you add a whole ten, like 10, 20, or 30, only the tens digit moves. The ones digit stays exactly the same. **Recap.** Split a number into tens and ones, then add or compare using that instead of counting one by one. ## Practice 17 questions on this page, each with its working shown. ## Needs first - [Number bonds](https://lightmysky.com/learn/mathematics/number-bonds-mt_s2mfRBoTal) - [The two digits of a two-digit number](https://lightmysky.com/learn/mathematics/the-two-digits-of-a-two-digit-number-mt_THl9GLxwoL) ## Opens up - [Place Value to 1000](https://lightmysky.com/learn/mathematics/place-value-to-1000-mt_98c2qwEF7Q)