Adding and subtracting tens mentally
Add and subtract a two-digit number and tens mentally and using concrete/pictorial representations
Teaching approaches
Gakuva’s recommended starting approach is selected. You can still compare every option.
1 approach
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
Learning resources
Reviewed external links that reinforce this concept. They do not replace Gakuva’s teaching approach.
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.
Proof: Save before-and-after snapshots of a tens change (for example 34→54) and a parent note of the mental “+10/−10” statement.
Base Ten Blocks
Virtual tens and ones for modeling ten more or ten less without counting up by ones.
Proof: Save a screenshot of tens rods changing by one rod and a parent note of the starting and ending totals.
Place Value Charts
Interactive place-value chart for seeing how the tens digit changes when adding or subtracting tens.
Proof: Save a chart screenshot showing a tens-digit change and a parent note explaining which place changed.
Explore the learning path
2 before · 1 after
This concept
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