---
title: "Fluent addition and subtraction"
description: "Recall and use addition and subtraction facts to 20 fluently, and derive and use related facts up to 100"
canonical: https://lightmysky.com/learn/mathematics/fluent-addition-and-subtraction-mt_3e_PQxwC12
source: https://lightmysky.com/learn/mathematics/fluent-addition-and-subtraction-mt_3e_PQxwC12.md
retrieved: 2026-11-12
---

> **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`.

# Fluent addition and subtraction

Recall and use addition and subtraction facts to 20 fluently, and derive and use related facts up to 100

Subject: Mathematics · Area: Addition & Subtraction · Ages 6 to 7
Page: https://lightmysky.com/learn/mathematics/fluent-addition-and-subtraction-mt_3e_PQxwC12

## Ready when they can

- Rapidly recall 7 + 8 = 15 and 15 − 8 = 7
- Use 6 + 4 = 10 to derive 60 + 40 = 100
- Derive 35 + 5 = 40 from knowledge that 5 + 5 = 10

## Lesson: Fast facts, big jumps

Practise facts to 20 so you can remember them more quickly. Use a drawing or a known fact when you need help. To make ten, split one number, keeping all its parts. Fill ten first, then add the rest. A double adds two equal groups. A near double adds one more than a double.

*(drawing: 8 + 5: split 5 into 2 and 3. Make 10, then add 3 to reach 13.)*

Addition joins two parts into a total. Subtraction can take either part from that total. If 8 + 5 = 13, then 13 − 5 = 8 and 13 − 8 = 5. Start subtraction with the total. Taking one part away leaves the other. Add the parts again to check.

**Example.** A ten is a group of ten ones. A two-digit number has tens on the left and ones on the right. Since 2 + 8 = 10, 2 tens plus 8 tens make 10 tens: 20 + 80 = 100. Change both parts to tens when using this fact. In 20 + 8, 2 tens and 8 ones make 28.

**Example.** Use subtraction facts with tens too. Since 9 − 3 = 6, 9 tens take away 3 tens leave 6 tens: 90 − 30 = 60. For a missing part in 30 + [ ] = 90, find 9 − 3 = 6. The missing part is 6 tens, or 60.

**Example.** For 37 + 3, split 37 into 30 and 7. Since 7 + 3 = 10, the ones make one new ten. Keep the 30 and join it to that ten: 30 + 10 = 40. For 37 + [ ] = 40, the same fact tells you to add 3.

When counting back, count moves, not the starting number. For 12 − 4, move to 11, 10, 9, then 8. Check with 8 + 4 = 12. Reaching 7 would take five moves. You can check addition with subtraction too: 8 + 4 = 12 matches 12 − 4 = 8.

**Recap.** Practise facts to 20. Use known facts to check answers, work with tens and reach the next ten.

*Lesson, questions and flashcards written for this learning dataset.*

## Practice

18 questions on this page, each with its working shown.

## Needs first

- [Addition and subtraction within 20](https://lightmysky.com/learn/mathematics/addition-and-subtraction-within-20-mt_m1W6nTQJ2b)

## Optional connections

- [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

- [Fluent addition and subtraction (age 9+)](https://lightmysky.com/learn/mathematics/fluent-addition-and-subtraction-age-9-mt_Yw1_4Nfsql)