Mathematics
Addition & Subtraction
Procedural
7–8 yrs
Mentally adding tens to 3-digit numbers
心算三位数加整十数
Description
Mentally add and subtract a three-digit number and tens
Mastery Evidence
- Calculate 345 + 40 mentally
- Calculate 462 − 30 mentally
- Explain that only the tens digit changes (unless bridging through a hundred)
Assessment Prompt
Can your child quickly work out '354 + 40' or '628 − 30' in their head — knowing that only the tens digit changes?
Prerequisites 2
The three digits of a three-digit number
三位数的十位心算加减法需要掌握三位数的位值概念
10 or 100 More or Less
在已有"多/少10"的基础上，扩展为加任意10的倍数
Unlocks 0
No follow-up topics
