# Find the hidden part

Reason about a missing part of a known whole.

## Try it

1. Look at the whole before it is covered.
2. What can you see? What is hidden?
3. Explain. Uncover and check.

Look at the whole before your adult covers part of it.

- The whole is 5. You can see 3. What is hidden?
- The whole is 4. You can see 1. What is hidden?

Explain before you uncover and check.

## Your materials

[Open the pupil workbook PDF](/files/c385c4cae385f0f332fd1c00d8e3dba4e2a5838fae4774b70df25e42e950768e). Use pages **15, 41, 42**.

Counters, part mat, folded paper cover.

## Teacher lesson plan

### Learning goal

Reason about a missing part of a known whole.

### Before teaching

Can represent joining and taking away with the selected quantities.

### Model

Show 5 counters, cover 2, and leave 3 visible. Ask what must be hidden and why. Uncover to check. Connect 3 + 2 = 5 and 5 - 3 = 2 without requiring formal algebra.

### Guide, then apply

Use different splits of a known whole, letting the child both hide and solve. Ask what information a partner needs. Record visible, hidden, and whole with drawings or numbers.

### Interpret the response

For the pupil examples, whole 5 with 3 visible has 2 hidden; whole 4 with 1 visible has 3 hidden. If the whole is forgotten, show it again and use a fixed whole card.

### Support

Use a smaller whole, leave outlines of the starting collection, or let the child physically remove the visible part from a matching set.

### Extend when ready

Explain a missing-change story: some counters leave and a known number remain. Compare more than one possible story for the same relationship.

### Fresh check

Show a whole of 4, cover 2, and ask how the child knows what is hidden without lifting the cover first. Listen for a relationship, not just a guess.

[Teacher plans PDF](/files/1f4985652f45f6b19ef743d7b27765081e2d637d0a001670faa74e59383c736a): page 15. Record exact support and revisit the idea later.

## Keep learning

[Next in this path: Build with shapes](/agent/docs/tk-lesson-shapes) · [Choose a learning path](/agent/docs/tk-learn)

## Publication details

| Field | Value |
|---|---|
| Material | Classroom lesson |
| Learning path | Numbers and reasoning |
| Lesson | 14 |
| Learners | California TK, ages 4–5 |
| Setting | Full classroom |
| Pacing | Teacher selects from observed prerequisites |
| Author | Arcomm |
| Edition | First edition, 2026-09-08 |
| Format | Markdown |
| Evidence status | Original synthesis; not outcome-validated |

## Sources and dates

- [CDE: Mathematics](https://www.cde.ca.gov/sp/cd/re/documents/ptklfmathdomain.pdf): current PTKLF edition. Retrieved 2026-09-08T03:44:00.628834+00:00.
- [CDE: Kindergarten Mathematics Framework](https://www.cde.ca.gov/ci/ma/cf/documents/mathfwkindergarten.pdf): K.CC.5 and K.OA.1–5; kindergarten extensions. Retrieved 2026-09-08T03:44:00.628834+00:00.

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## Revisions

[Revision history](/agent/docs/tk-lesson-missing-part/history)