Fluent adding and subtracting within 20
Fluently add and subtract within 20 using mental strategies; know from memory all sums of two one-digit numbers
Lesson
Set out your lesson
“Fluent adding and subtracting within 20 means quick, sensible mental strategies for sums and differences within 20—including known one-digit sums. We will practice one make-ten strategy, one related subtraction, then check a fresh fact.”
Bring to the table
- Twenty counters in two colours
- A few flash cards within 20 (8+7, 14−6, 9+6)
- Optional: adult-previewed Illustrative Mathematics companion after the table demo
Extra for the adult
Worked example. 8+7: make ten with 8+2, then add 5 to get 15. Related: 15−7=8.
Optional challenge. For Fluent adding and subtracting within 20, give three rapid facts without counters, then prove one with make-ten.
What to notice. Keep one parent note: facts; strategies; support used. This session samples fluency practice, not mastery of every fact within 20.
Share and support
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Teaching approaches
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1 approach
Fluent adding and subtracting within 20 means quick, sensible mental strategies for sums and differences within 20—including known one-digit sums. We will practice one make-ten strategy, one related subtraction, then check a fresh fact.
Spend about 12 minutes building fluency within 20 with one clear strategy, then checking a new fact.
Family records and proof options
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Practice this concept
Start practiceFluent add/subtract within 20 practice
Use mental strategies for sums and differences within 20.
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
Hitting The Target Number
Before you open · source notes
Number cards 1–10 form target totals from 10 through 20 by addition or subtraction, with a spoken mental strategy. Keep the selected computations within 20. There is no automatic score; an adult or partner checks the work.
Free, no sign-in. Use the student view with your child.
Before you openHandwritten number cards are an original Gakuva family adaptation, not a feature of the website. The optional PDF of cards was not fetched or tested.
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 2026-11-10 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. “Hitting The Target Number.” 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
- Answer any single-digit addition fact within 3 seconds
- Recall subtraction facts within 20 from memory (e.g. 15 − 8 = 7)
- Use known addition facts to derive related subtraction facts rapidly
“Can your child instantly recall all the single-digit addition facts — like '7 + 8 = 15' — without needing to count or think for more than a second?”
Curriculum record
- Type
- Procedural
- Subject
- Mathematics
- Domain
- Addition & Subtraction
- Age range
- Ages 7–8
Standards