# X04 · Optional projects job

Four kits need 19 labels each. Explain two efficient strategies and show why both fit.

Use scrap paper or a private explanation. No purchase, household information or public performance.

## Adult teaching after an own try

### Answer

4 × (20 − 1) = 80 − 4 = 76; or double19=38,double38=76.

### Why

Choose and connect efficient representations, not speed.

[Plan Bench](../tool/index.html) · [Adult start](../teacher/START-HERE.html)