Adding and subtracting tens mentally
Add and subtract a two-digit number and tens mentally and using concrete/pictorial representations
Entire curriculum
1858 concepts · 9 subjects
Share and support
Compare teaching approaches
Teaching approaches
Gakuva’s recommended starting approach is selected. You can still compare every option.
1 approach
Adding and subtracting tens mentally means changing a two-digit number by a multiple of ten without recounting every one. 45 + 30 changes only the tens digit (4 becomes 7) because three tens were added; the ones stay 5. 82 − 40 removes four tens; the ones stay 2. We will build one model, then try mental answers with a quick check.
Spend about 12 minutes adding and subtracting multiples of ten from two-digit numbers, first with tens bundles or drawings, then mentally, explaining which digit changes.
Family records and proof options
Keep a record of your learning
Save photos, notes, and attendance. Export a proof packet for compliance or portfolio reviews.
Learning resources
Extra practice links — they do not replace Gakuva’s teaching approach.
The Math Learning Center · Practice link — not the full lesson
Number Pieces
Before you open · source notes
Adult-guided base-ten pieces for adding or subtracting tens mentally. Build a two-digit number, add/remove ten-rods, and say the new total.
Free · no login
Before you openSave before-and-after snapshots of a tens change (for example 34→54) and a parent note of the mental “+10/−10” statement.
Opening this link does not save learning or assess mastery.
Source, access and review notes
Unknown — link only
Toy Theater · Practice link — not the full lesson
Base Ten Blocks
Before you open · source notes
Virtual tens and ones for modeling ten more or ten less without counting up by ones.
Free · no login · ads
Before you openSave a screenshot of tens rods changing by one rod and a parent note of the starting and ending totals.
Opening this link does not save learning or assess mastery.
Source, access and review notes
Unknown — link only
Topmarks · Practice link — not the full lesson
Place Value Charts
Before you open · source notes
Interactive place-value chart for seeing how the tens digit changes when adding or subtracting tens.
Free · no login · ads
Before you openSave a chart screenshot showing a tens-digit change and a parent note explaining which place changed.
Opening this link does not save learning or assess mastery.
Source, access and review notes
Unknown — link only
Check understanding
- Calculate 45 + 30 = 75 mentally
- Calculate 82 − 40 = 42 mentally
- Explain that only the tens digit changes when adding/subtracting tens
“Can your child quickly work out '54 + 30' or '78 − 20' in their head — knowing that only the tens digit changes?”
Curriculum record
- Type
- Procedural
- Subject
- Mathematics
- Domain
- Addition & Subtraction
- Age range
- Ages 6–9
Standards