# 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).

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