Adding and subtracting tens mentally
Add and subtract a two-digit number and tens mentally and using concrete/pictorial representations
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Teaching Table · Plan outline
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“Can your child quickly work out '54 + 30' or '78 − 20' in their head — knowing that only the tens digit changes?”
Full guide and materials
- Activity. Add and subtract a two-digit number and tens mentally and using concrete/pictorial representations
What to notice. Calculate 45 + 30 = 75 mentally • Calculate 82 − 40 = 42 mentally • Explain that only the tens digit changes when adding/subtracting tens
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Can your child quickly work out '54 + 30' or '78 − 20' in their head — knowing that only the tens digit changes?
Add and subtract a two-digit number and tens mentally and using concrete/pictorial representations
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Learning resources
Reviewed external links that reinforce this concept. They do not replace Gakuva’s teaching approach.
The Math Learning Center · Practice link — not the full lesson
Number Pieces
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
Review and open practice
Save 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.
Open practice (new tab)Source, access and review 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.
Save before-and-after snapshots of a tens change (for example 34→54) and a parent note of the mental “+10/−10” statement.
Free · no login
Unknown — link only
Toy Theater · Practice link — not the full lesson
Base Ten Blocks
Virtual tens and ones for modeling ten more or ten less without counting up by ones.
Free · no login · ads
Review and open practice
Save 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.
Open practice (new tab)Source, access and review notes
Virtual tens and ones for modeling ten more or ten less without counting up by ones.
Save a screenshot of tens rods changing by one rod and a parent note of the starting and ending totals.
Free · no login · ads
Unknown — link only
Topmarks · Practice link — not the full lesson
Place Value Charts
Interactive place-value chart for seeing how the tens digit changes when adding or subtracting tens.
Free · no login · ads
Review and open practice
Save 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.
Open practice (new tab)Source, access and review notes
Interactive place-value chart for seeing how the tens digit changes when adding or subtracting tens.
Save a chart screenshot showing a tens-digit change and a parent note explaining which place changed.
Free · no login · ads
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 6–7
Standards