# Open-ten plan: choose a useful split

Show the same whole with one fewer full ten. Use 39 safe pieces or original marks. A supplied ordinary teaching account is 30 + 9 = 39; inspect its members, then choose another valid split of the same whole. A job may suit unequal parts.

1. Show what each part contains.
2. Check that every object has one place.
3. Choose a split that suits this job. Show a reason and a possible revision.

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[Full daily plan](../teacher/day-50.md) gives today's exact reasoning and next instruction. This is an ordinary practice model, not a reserved fresh answer. If the total is too large, choose and label a smaller actual collection while keeping the partition purpose. Adult movement follows the child's decisions. Supplied counts are support, not evidence of independently finding that count. Choose the next teaching by the missing component: coverage, unit value, replacement, changed parts, or justified keep/repair. Use a different small example and then a new case, not the same memorised answer.

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