Mentally adding tens to 3-digit numbers
Mentally add and subtract a three-digit number and tens
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Teaching Table
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“Can your child quickly work out '354 + 40' or '628 − 30' in their head — knowing that only the tens digit changes?”
Full guide and materials
- Activity. Mentally add and subtract a three-digit number and tens
What to notice. Calculate 345 + 40 mentally • Calculate 462 − 30 mentally • Explain that only the tens digit changes (unless bridging through a hundred)
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Can your child quickly work out '354 + 40' or '628 − 30' in their head — knowing that only the tens digit changes?
Mentally add and subtract a three-digit number and tens
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Check understanding
- Calculate 345 + 40 mentally
- Calculate 462 − 30 mentally
- Explain that only the tens digit changes (unless bridging through a hundred)
“Can your child quickly work out '354 + 40' or '628 − 30' in their head — knowing that only the tens digit changes?”
Curriculum record
- Type
- Procedural
- Subject
- Mathematics
- Domain
- Addition & Subtraction
- Age range
- Ages 7–8
Standards