# Day 17 — Eighteen and nineteen

**25 minutes · AC9MFN01 (18–19 representation and order), AC9MFN03 (count and compare 18/19); partial practice · educator review pending**

**Success today:** The child builds 18 and 19, counts each set, matches the numerals, and places 18 between 17 and 19.

**Prepare per pair:** two ten-frames, 19 counters, cards 17–19 and path; see [print-aids.md](print-aids.md). Keep the second frame orientation consistent.

1. **Reconnect, 3 min.** Show 17 as ten and seven. Ask what one extra object would make; let the child test the idea.
2. **Model, 6 min.** Fill ten spaces and eight more. Say, “This shows eighteen; I can see two empty spaces in the second frame. I will count to confirm.” Show `18`. Add one object. “Now there is one empty space and nineteen objects.” Count and show `19`. Compare: 19 has one more object than 18.
3. **Play: museum cases, 9 min.** One partner arranges 18 pretend labels across two cases; another checks and chooses `18`. Add one label for `19`, then swap. Variants: 18/19 bike-repair job cards or 18/19 weather-station marks. If a child invents a scene, keep the counts unchanged for the check.
4. **Independent try, 4 min.** Hand the child an uncounted pile of 19 objects and cards `17, 18, 19`. “Make eighteen, choose its numeral, then show the next number.” Accept counting all or ten-and-more with a verification count.
5. **Check and close, 3 min.** Lay `17, [empty], 19`. “Which card is missing? How do you know?” **Key:** 18; `17, 18, 19` is the order; 19 is one more than 18.

**If the child infers 18 solely from two empty spaces:** Ask them to verify that the first frame really holds ten and the second holds eight. An empty-space shortcut is only reliable if the frame and its filling are known. If `18` and `19` are reversed, place each beside its checked collection and compare the one extra object.

**Access and record:** Offer high-contrast or tactile cards, a raised second frame, hand-sized counters, spoken descriptions, and directed partner placement. Record total/count match for 18 and 19, missing-number reasoning, counting accuracy and prompt level.