MathGrade 2ages 7–8
🔟 Subtracting tens
A child who solves 50 − 20 incorrectly, either by touching the ones digit or by adding the tens together, hasn't yet treated a "ten" as one countable bundle rather than two separate digits.
Try this lesson freeNo card needed. The first lesson is free.
Download on the App StoreWhat your child learns
- A whole ten is a bundle. You take bundles away.
- 50 − 20 = 30. Five bundles minus two = three.
- If there are ones, they stay: 54 − 20 = 34.
- Not 50 − 20 = 70. That would be adding.
The mistake most kids make here
Taking from the ones too, or adding the tens.
Try one question
50 − 20
- 30
- 70
- 20
Answer
30 — Yes. Three bundles are left.
How Maya teaches it
Your child tells Maya what they did in class. She teaches this topic at her desk, asks questions with tappable answers, and when the answer is wrong she explains why that answer was tempting instead of saying “try again”. She remembers what did not land and comes back to it.
Your child has it when they can: 50 − 20 — the ones do not move.
How to help at home
When numbers are shown as separate digits on paper, it's easy to lose the idea that 50 is five whole bundles of ten, not a 5 and a 0 that can each be changed on their own.
Use ten small bundles — ten straws held with a rubber band, or ten coins in a cup, five bundles per pile. Lay out five bundles for 50, ask your child to remove two whole bundles for the 20, and count what's left: three bundles, or 30.
If your child's answer touches the ones digit when there isn't one to touch, or grows the number instead of shrinking it, ask: "are we removing whole bundles, or messing with a single straw?" That question brings the ones back into focus, if there are any.
A sign they've got it: they can solve 54 − 20 by leaving the 4 loose ones untouched and only removing bundles, arriving at 34 without hesitation.
Questions parents ask
- Why does my child change the ones digit when subtracting tens?
- Digits on paper can look interchangeable to a child who hasn't yet connected the tens place to an actual bundle of ten objects. Working with real bundles makes it clear that only whole-ten amounts move.
- What if there's a number in the ones place, like in 54 − 20?
- The ones stay exactly where they are — only the tens are being removed. Practicing with a mix of loose objects and bundles helps a child see why the loose ones aren't affected.
- Should I introduce column subtraction with borrowing yet?
- Not until subtracting whole tens without borrowing feels automatic. Borrowing adds a layer of complexity that's easier once the basic bundle idea is solid.
- How does Maya teach subtracting tens?
- Maya has the child work with bundled groups of ten before moving to digits on paper, so "ten" stays a countable amount rather than an abstract symbol.
No card needed. The first lesson is free.
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