整十数相减

运用位值策略计算整十数减整十数（10～90）。

Subtract multiples of 10 (10–90) from multiples of 10 using place value strategies

学习证据 / Evidence

• 计算出 70 − 30 = 40
• 用十位积木块表示 80 − 50 = 30
• 解释整十数相减就像用十位上的数字相减

• Calculate 70 − 30 = 40
• Use base-ten blocks to show 80 − 50 = 30
• Explain that subtracting tens is like subtracting the tens digits

评估问题 / Assessment

{{name}}能通过想一想还剩几个十，快速口算出“80 − 50”或“70 − 40”吗？

Can {{name}} quickly work out '80 − 50' or '70 − 40' in their head by thinking about how many tens are left?