三位数加整十数的口算
Mentally adding tens to 3-digit numbers
心算三位数与整十数的加法和减法
Mentally add and subtract a three-digit number and tens
学习证据 / Evidence
- 口算 345 + 40
- 口算 462 − 30
- 解释只有十位上的数字会改变（除非需要进位到百位）
- Calculate 345 + 40 mentally
- Calculate 462 − 30 mentally
- Explain that only the tens digit changes (unless bridging through a hundred)
评估问题 / Assessment
{{name}}能快速心算出“354 + 40”或“628 − 30”，并知道只有十位上的数字会改变吗？
Can {{name}} quickly work out '354 + 40' or '628 − 30' in their head — knowing that only the tens digit changes?