--- title: "Length word problems within 100" description: "Solve word problems involving lengths within 100, using addition and subtraction with drawings and equations" canonical: https://lightmysky.com/learn/mathematics/length-word-problems-within-100-mt_DLcEzmmj2r source: https://lightmysky.com/learn/mathematics/length-word-problems-within-100-mt_DLcEzmmj2r.md retrieved: 2026-09-02 --- > **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`. # Length word problems within 100 Solve word problems involving lengths within 100, using addition and subtraction with drawings and equations Subject: Mathematics · Area: Measurement · Ages 7 to 8 Page: https://lightmysky.com/learn/mathematics/length-word-problems-within-100-mt_DLcEzmmj2r ## Ready when they can - Solve 'The rope is 45 cm long. I cut off 18 cm. How long is it now?' - Draw a diagram (e.g. a ruler drawing) to represent a length word problem - Write an equation with a symbol for the unknown to represent the problem ## Lesson: Solving length word problems Word problems about length ask you to find a missing length. Some problems make a length longer, so you add. Others make a length shorter, so you subtract. Read the problem carefully to decide which one it is. *(drawing: The rope starts at 45 cm. Cutting off 18 cm hops it back to 27 cm.)* **Example.** A ribbon is 62 cm long. Mia glues on another piece that is 15 cm long. The ribbon gets longer, so you add: 62 + 15 = 77. The ribbon is now 77 cm long. Drawing helps. Draw a number line and mark where the length starts. To add a piece, hop forward. To cut a piece off, hop back. The number you land on is the new length, and the size of the hop is the piece. Sometimes the missing number is the piece itself. Write it as a letter, like n. A rope is 80 cm and 55 cm is left after a cut, so 80 − n = 55. The letter stands for the piece you cut off. **Recap.** Decide if the length grows or shrinks, write an equation with a symbol for the missing number, then solve it. ## Practice 8 questions on this page, each with its working shown. ## Needs first - [Fluent adding and subtracting within 100](https://lightmysky.com/learn/mathematics/fluent-adding-and-subtracting-within-100-mt_cChv2j_-Da) - [Comparing lengths by measuring](https://lightmysky.com/learn/mathematics/comparing-lengths-by-measuring-mt_xWg0lI_gG4) ## Opens up - [Working with money](https://lightmysky.com/learn/mathematics/working-with-money-mt_iQYPw8bMfN)