Mental addition and subtraction (age 7+)
Mentally add and subtract a three-digit number and ones
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Teaching Table
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“Can your child work out '436 + 7' or '521 − 8' in their head — keeping the hundreds and tens unchanged while adjusting just the ones?”
Full guide and materials
- Activity. Mentally add and subtract a three-digit number and ones
What to notice. Calculate 345 + 7 mentally • Calculate 462 − 5 mentally • Explain that only the ones digit changes (unless bridging through a ten)
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Can your child work out '436 + 7' or '521 − 8' in their head — keeping the hundreds and tens unchanged while adjusting just the ones?
Mentally add and subtract a three-digit number and ones
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Check understanding
- Calculate 345 + 7 mentally
- Calculate 462 − 5 mentally
- Explain that only the ones digit changes (unless bridging through a ten)
“Can your child work out '436 + 7' or '521 − 8' in their head — keeping the hundreds and tens unchanged while adjusting just the ones?”
Curriculum record
- Type
- Procedural
- Subject
- Mathematics
- Domain
- Addition & Subtraction
- Age range
- Ages 7–8
Standards