Mental addition and subtraction (age 9+)
Add and subtract numbers mentally with increasingly large numbers, using place-value knowledge and derived facts
Lesson
Set out your lesson
“Mental addition and subtraction (age 9+) means practising the idea at the table with counters or paper models and one clear check. We will demo once, then your child tries.”
Bring to the table
- 20 counters
- Paper and pencil
Extra for the adult
Worked example. Start with 12 counters, remove 4, 8 remain. Write 12 − 4 = 8.
Optional challenge. For Mental addition and subtraction (age 9+), add one harder example after success.
What to notice. Keep one parent note: examples tried; results; support used. This session samples Mental addition and subtraction (age 9+), not mastery.
Share and support
Family records and proof options
Keep a record of your learning
Save photos, notes, and attendance. Export a proof packet for compliance or portfolio reviews.
Practice this concept
Start practiceMental addition and subtraction (age 9+) practice
Practice key ideas from Mental addition and subtraction (age 9+).
Free · no login · no ads · Practice answers and completion are not saved. Parent observation remains the lesson record.
Learning resources
Extra practice links — they do not replace Gakuva’s teaching approach.
Illustrative Mathematics · Practice link — not the full lesson
Cave Game Subtraction
Before you open · source notes
Cave-game subtraction supports mental addition and subtraction. Not every calculator check.
Free, no sign-in. A teacher solution is on the same page, so use the student view with your child.
Before you openAsk the learner to solve one subtraction as an unknown addend and say the strategy.
Opening this link does not save learning or assess mastery.
Source, access and review notes
Public Illustrative Mathematics task page. The .html address responds HTTP 308 to this URL. An anonymous GET of this URL on 2026-11-12 returned HTTP 200 with no login or payment prompt. Where a teacher solution is present, it is on the same page as the student task; this check did not find a separate locked student view. An adult can use the student view section and should not read a solution aloud. Advertising was not observed in the fetched HTML text; that is not a browser, device, or ad-free guarantee. This is a paper or discussion task, not an automatically marked interactive game. Opening the link does not save practice or assess mastery. Diagrams on the page use missing or filename-only alt text, so they are not an accessible image equivalent. Accessibility still depends on an adult describing the picture.
Illustrative Mathematics. “Cave Game Subtraction.” Licensed CC BY-NC-SA 4.0. External task; Gakuva does not copy, host, embed, or redistribute it.
CC BY-NC-SA 4.0 — link only
Check understanding
- Mentally calculate 45,000 + 8,000
- Mentally subtract 3,200 from 10,000 by counting up
- Use near-doubles: 2,500 + 2,600 = 5,100
“Can your child work out something like '4,700 − 1,300' in their head using what they know about place value — without needing to write it all out?”
Curriculum record
- Type
- Procedural
- Subject
- Mathematics
- Domain
- Addition & Subtraction
- Age range
- Ages 9–10
Standards