--- title: "Addition and subtraction within 1000" description: "Add and subtract within 1000 using concrete models, drawings, and strategies based on place value; understand composing and decomposing tens and hundreds" canonical: https://lightmysky.com/learn/mathematics/addition-and-subtraction-within-1000-mt_ewmuMMPAzP source: https://lightmysky.com/learn/mathematics/addition-and-subtraction-within-1000-mt_ewmuMMPAzP.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`. # Addition and subtraction within 1000 Add and subtract within 1000 using concrete models, drawings, and strategies based on place value; understand composing and decomposing tens and hundreds Subject: Mathematics · Area: Addition & Subtraction · Ages 7 to 8 Page: https://lightmysky.com/learn/mathematics/addition-and-subtraction-within-1000-mt_ewmuMMPAzP ## Ready when they can - Add two three-digit numbers using base-ten blocks or drawings, composing a ten or hundred when necessary - Subtract three-digit numbers, decomposing a ten or hundred when necessary - Relate the concrete/drawn strategy to a written method and explain why it works ## Lesson: Adding and subtracting big numbers You already know how to add and subtract numbers up to 100. Big numbers work the same way, with one more place: hundreds. Line up the places and start with the ones. If a place adds up to 10 or more, trade 10 of them for 1 of the next place. If a top digit is too small to take away from, trade 1 from the next place for 10. *(drawing: 347 is 3 hundreds, 4 tens, and 7 ones.)* **Example.** Add 358 + 267. Ones: 8 + 7 = 15, so write 5 and carry 1 ten. Tens: 5 + 6 + 1 = 12, so write 2 and carry 1 hundred. Hundreds: 3 + 2 + 1 = 6. The answer is 625. *(drawing: 468 + 238: 16 ones makes 1 ten and 6 ones, then 10 tens makes 1 hundred. The total is 706.)* *(drawing: With zero tens, exchange a hundred first, then exchange one ten for ten ones.)* **Example.** Subtract 604 - 287. There are 0 tens, so first exchange 1 hundred for 10 tens. Then exchange 1 ten for 10 ones: 5 hundreds, 9 tens and 14 ones. Now 14 - 7 = 7, 9 - 8 = 1 and 5 - 2 = 3. The answer is 317. Exchanging is also called borrowing. Drawing hundreds, tens, and ones as blocks shows the trades. Ten ones become one ten, and ten tens become one hundred. For example, 11 tens can trade 10 tens for 1 hundred, leaving 1 ten. Subtraction trades the other way: 1 hundred becomes 10 tens. The written method records the same trades with digits. **Recap.** Add or subtract one place at a time, and trade 10 ones for a ten or 10 tens for a hundred whenever you need to. ## Practice 17 questions on this page, each with its working shown. ## Needs first - [The three digits of a three-digit number](https://lightmysky.com/learn/mathematics/the-three-digits-of-a-three-digit-number-mt_aPBzD28_mT) - [Fluent adding and subtracting within 100](https://lightmysky.com/learn/mathematics/fluent-adding-and-subtracting-within-100-mt_cChv2j_-Da) ## Opens up - [Fluent adding and subtracting within 1000](https://lightmysky.com/learn/mathematics/fluent-adding-and-subtracting-within-1000-mt_HFRYjTb-Z5) - [Estimating by rounding](https://lightmysky.com/learn/mathematics/estimating-by-rounding-mt_QaYfeVL-0C) - [Adding and subtracting (age 7+)](https://lightmysky.com/learn/mathematics/adding-and-subtracting-age-7-mt_SrrsLiJkr3)