Addition and subtraction within 20
Add and subtract within 20 using strategies such as making ten, decomposing a number leading to ten, and using known facts
Lesson
Set out your lesson
“Addition and subtraction within 20 means solving sums and differences to 20 with strategies—not only counting every object from one. Making ten (8 + 5 → 8 + 2 + 3), decomposing to reach ten (13 − 4 → 13 − 3 − 1), and using a known fact (9 + 9 = 18 so 9 + 8 = 17) are the moves. We will model one of each, then try a short mixed set.”
Bring to the table
- About 20 large counters, blocks, or dried beans (parent keeps tiny pieces away from mouths)
- Paper and pencil
Extra for the adult
Worked example. 8 + 5 = 13 by making ten (8 + 2 + 3). 13 − 4 = 9 by decomposing to ten (13 − 3 − 1). 9 + 8 = 17 from the known double 9 + 9 = 18. Strategies replace recounting every object from one.
Optional challenge. For Addition and subtraction within 20, solve 9 + 7 and 16 − 9 using two different strategies and explain which felt faster. Optional: invent one short kitchen story that needs a within-20 make-ten sum.
What to notice. Keep one parent note: equations tried; strategies named or shown; answers; support used. A photo of counters alone does not show the strategy talk. This session samples a few facts, not mastery of every combination within 20.
Share and support
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Teaching approaches
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1 approach
Addition and subtraction within 20 means solving sums and differences to 20 with strategies—not only counting every object from one. Making ten (8 + 5 → 8 + 2 + 3), decomposing to reach ten (13 − 4 → 13 − 3 − 1), and using a known fact (9 + 9 = 18 so 9 + 8 = 17) are the moves. We will model one of each, then try a short mixed set.
Spend about 12 minutes practising addition and subtraction within 20 with counters and written equations, using make-ten and related-fact strategies, then checking two fresh problems.
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Learning resources
Extra practice links — they do not replace Gakuva’s teaching approach.
Topmarks · Practice link — not the full lesson
Robot Addition
Before you open · source notes
Addition matching with an Addition to 20 mode for facts within 20. Pair with adult talk about making ten or using a known fact when a level feels hard.
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Before you openSave a screenshot from Addition to 20 mode plus a parent note describing one making-ten or known-fact strategy the learner used.
Opening this link does not save learning or assess mastery.
Source, access and review notes
Unknown — link only
Visnos · Practice link — not the full lesson
Addition & Subtraction Facts
Before you open · source notes
Number-line visualization of addition and subtraction facts through 20 for connecting equations to quantities.
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Before you openSave a screenshot of an equation within 20 and a parent note that the learner explained the move on the number line.
Opening this link does not save learning or assess mastery.
Source, access and review notes
Unknown — link only
Toy Theater · Practice link — not the full lesson
Math Mine Addition Subtraction
Before you open · source notes
Solve addition and subtraction equations and clear numbered blocks. Keep problems within 20 and pause to name the strategy used.
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Before you openSave a Problems Solved screenshot plus a parent note of correct addition and subtraction examples within 20.
Opening this link does not save learning or assess mastery.
Source, access and review notes
Unknown — link only
Check understanding
- Solve 8 + 6 using making ten, e.g. on a real or on-screen double ten frame: 8 + 2 + 4 = 14
- Solve 13 − 4 by decomposing: 13 − 3 − 1 = 9
- Use a known fact (8 + 4 = 12) to derive 12 − 8 = 4
“If your child needs to work out '8 + 6', can they split the 6 into 2 + 4, use the 2 to fill up to 10, then add the remaining 4 to get 14?”
Curriculum record
- Type
- Procedural
- Subject
- Mathematics
- Domain
- Addition & Subtraction
- Age range
- Ages 6–8
Standards