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SUBJECTNEST · YEAR 2 MATHEMATICS · WEEKS 9–10 · day-48
Day 48 · Choose a way to add or subtract
Try: “Which way helps with this problem?”
Adult teaching purpose: One/two-digit addition/subtraction, part-whole reasoning and
taught facts≤20; AC9M2N04/A02 components.
1 · Prepare and invite. Prepare ordinary19+6 and32−8 fictional quantities, broad marks or a
blank strategy space. Fact support can be offered after the first method and named. No
race/timer/public ranking. Recognise+as join and−as remove/difference in context; a
smaller10−3 taught example can help with prerequisites but gives narrower evidence.
2 · Model a different small example. Model unrelated28+7: add2 to reach30, then5
more=35. Check by partitioning20+8+7=20+15=35. For a different
subtraction26−4,26−4=22 by ones. Say the child can choose counting on/back, tens
bridge, drawing, partition or another valid strategy; the displayed method is not
compulsory.
3 · Guide one attempt. Use19+6 together. Child chooses bridge20(+1 then+5), known9+6
with ten, or counted units. Keep6 split as1+5; do not add1 then6. For32−8, bridge32−2=30
then−6=24, or count up24→32 to check8. Ask what each part represents.
4 · Your own useful turn. Choose an ordinary context C14–C18 and make an own number
sentence, representation and explained answer. Keep the question with the numeral. An
adult can draw exactly as directed; calculator checking after the method is labelled
software help. Optional fact practice: choose8+7=15 then related15−8=7, explain the link
rather than recite fast.
5 · Observe and record. Keep the actual choice, representation, method and meaning
before a correction. Distinguish a source fact, child decision, adult reading/scribing/handling
and mathematical hint. Observe strategy conservation and operation meaning. If bridge
double-counts, teach splitting5 as2+3 using unrelated18+5. If subtraction direction
reverses, act/draw a different fictional collection11 with3 removed. If secure, ask for a
second method and a meaningful inverse check. Correct numeral with no accessible
explanation is limited evidence, not proof of fluency across facts.
6 · Teach next and revisit. Choose just the applicable next teaching in step5, on a different
ordinary source; then offer a new question after an actual interval. Record what happened
rather than completing all branches. Read the three participation choices
(../ROUTES.md#day-48); parent offer (../family/home-48.md) is optional. A short useful
attempt can replace a long sheet. Full source/rights and curriculum evidence stay in the
adult mapping (../curriculum/MAPPING.md) and notice (../legal/NOTICE.md).
Original SubjectNest educational material ©2026 SubjectNest contributors. CC BY4.0; full
portable conditions and outside exceptions: notice (../legal/NOTICE.md).
SubjectNest / NeuroForge 2026 · Original expression CC BY 4.0; separate terms accompany.
Keep complete notices and inert source/rights PDF attachments.
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# Day 48 · Choose a way to add or subtract

**Try:** “Which way helps with this problem?”

**Adult teaching purpose:** One/two-digit addition/subtraction, part-whole reasoning and taught facts≤20; AC9M2N04/A02 components.

**1 · Prepare and invite.** Prepare ordinary19+6 and32−8 fictional quantities, broad marks or a blank strategy space. Fact support can be offered after the first method and named. No race/timer/public ranking. Recognise+as join and−as remove/difference in context; a smaller10−3 taught example can help with prerequisites but gives narrower evidence.

**2 · Model a different small example.** Model unrelated28+7: add2 to reach30, then5 more=35. Check by partitioning20+8+7=20+15=35. For a different subtraction26−4,26−4=22 by ones. Say the child can choose counting on/back, tens bridge, drawing, partition or another valid strategy; the displayed method is not compulsory.

**3 · Guide one attempt.** Use19+6 together. Child chooses bridge20(+1 then+5), known9+6 with ten, or counted units. Keep6 split as1+5; do not add1 then6. For32−8, bridge32−2=30 then−6=24, or count up24→32 to check8. Ask what each part represents.

**4 · Your own useful turn.** Choose an ordinary context C14–C18 and make an own number sentence, representation and explained answer. Keep the question with the numeral. An adult can draw exactly as directed; calculator checking after the method is labelled software help. Optional fact practice: choose8+7=15 then related15−8=7, explain the link rather than recite fast.

**5 · Observe and record.** Keep the actual choice, representation, method and meaning before a correction. Distinguish a source fact, child decision, adult reading/scribing/handling and mathematical hint. Observe strategy conservation and operation meaning. If bridge double-counts, teach splitting5 as2+3 using unrelated18+5. If subtraction direction reverses, act/draw a different fictional collection11 with3 removed. If secure, ask for a second method and a meaningful inverse check. Correct numeral with no accessible explanation is limited evidence, not proof of fluency across facts.

**6 · Teach next and revisit.** Choose just the applicable next teaching in step5, on a different ordinary source; then offer a new question after an actual interval. Record what happened rather than completing all branches. Read the three [participation choices](../ROUTES.md#day-48); [parent offer](../family/home-48.md) is optional. A short useful attempt can replace a long sheet. Full source/rights and curriculum evidence stay in the adult [mapping](../curriculum/MAPPING.md) and [notice](../legal/NOTICE.md).

Original SubjectNest educational material ©2026 SubjectNest contributors. CC BY4.0; full portable conditions and outside exceptions: [notice](../legal/NOTICE.md).