--- title: "One-to-one counting" description: "One-to-one correspondence when counting objects: each object is paired with exactly one number name" canonical: https://lightmysky.com/learn/mathematics/one-to-one-counting-mt_WcfaSfVT33 source: https://lightmysky.com/learn/mathematics/one-to-one-counting-mt_WcfaSfVT33.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`. # One-to-one counting One-to-one correspondence when counting objects: each object is paired with exactly one number name Subject: Mathematics · Area: Counting & Cardinality · Ages 4 to 6 Page: https://lightmysky.com/learn/mathematics/one-to-one-counting-mt_WcfaSfVT33 ## Ready when they can - Point to or touch each object exactly once while saying number names - Do not skip objects or double-count when counting a set - Recognise an error when someone counts an object twice ## Lesson: Counting one by one When you count, every thing gets exactly one number. Touch it, say the number, move on. If you count a thing twice, your count comes out too big. If you skip a thing, your count comes out too small. *(drawing: Touch each star once: 1, 2, 3, 4, 5.)* **Example.** Leo counts his apples. He touches each apple one time and says 1, 2, 3, 4. Four apples. **Tip.** If you touch a thing twice, it gets two numbers, and the count comes out too big. If you skip a thing, it gets no number, and the count comes out too small. One touch, one number. **Recap.** One thing, one number. Never skip, never count twice. ## Practice 17 questions on this page, each with its working shown. ## Opens up - [How Many in Total?](https://lightmysky.com/learn/mathematics/how-many-in-total-mt_dmNvjroCPT) - [Counting objects to 20](https://lightmysky.com/learn/mathematics/counting-objects-to-20-mt_yqAL6O5i_v)