Mental addition and subtraction (age 6+)
Add and subtract a two-digit number and ones mentally and using concrete/pictorial representations
Lesson
Set out your lesson
“Mental addition and subtraction (age 6+) in this lesson means adding or subtracting a single-digit number to or from a two-digit number—first with a concrete or picture model, then mentally. 46 + 5 and 46 − 5 stay focused on the ones, with composing or decomposing a ten when needed. We will model, fade the model, then check two fresh items.”
Bring to the table
- About 40 large counters or a quick tens-and-ones sketch pad (parent keeps tiny pieces away from mouths)
- Paper and pencil
Extra for the adult
Worked example. 46 + 5 = 51 (six ones and five ones make eleven ones → one more ten and one one). 46 − 5 = 41 (ones decrease by five; tens unchanged). Concrete or pictorial models support the mental step.
Optional challenge. For Mental addition and subtraction (age 6+), solve 68 + 7 and 68 − 9 mentally and explain when a ten had to be made or broken. Optional: invent one short score-keeping story that adds or subtracts ones from a two-digit total.
What to notice. Keep one parent note: equations tried; answers; model vs mental; compose/decompose moments; support used. A photo of counters alone does not show the mental step. This session samples a few items, not fluency for every case.
Share and support
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Teaching approaches
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1 approach
Mental addition and subtraction (age 6+) in this lesson means adding or subtracting a single-digit number to or from a two-digit number—first with a concrete or picture model, then mentally. 46 + 5 and 46 − 5 stay focused on the ones, with composing or decomposing a ten when needed. We will model, fade the model, then check two fresh items.
Spend about 12 minutes adding and subtracting ones from two-digit numbers with counters or sketches, writing equations, then answering two mental items.
Family records and proof options
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Learning resources
Extra practice links — they do not replace Gakuva’s teaching approach.
Illustrative Mathematics · Practice link — not the full lesson
Making a ten
Before you open · source notes
Making a ten supports mental addition and subtraction within 20. Not every multi-digit written method.
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 make a ten to solve one addition fact and say the helper ten used.
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. “Making a ten.” 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
- Calculate 36 + 7 = 43 using objects or mentally
- Calculate 52 − 4 = 48 using a number line or mentally
- Explain bridging through 10 when adding ones to a two-digit number
“Can your child work out '36 + 7' or '42 − 5' in their head — keeping the tens in place and only adjusting the ones?”
Curriculum record
- Type
- Procedural
- Subject
- Mathematics
- Domain
- Addition & Subtraction
- Age range
- Ages 6–10
Standards