分组凑整相加
Grouping numbers to add
理解并运用加法结合律：计算三个数相加时，可以先把其中任意两个数加起来。
Understand and apply the associative property of addition: when adding three numbers, any two can be added first
学习证据 / Evidence
- 先算 6 + 4 = 10，再算 2 + 10 = 12，从而算出 2 + 6 + 4 的结果。
- 解释把加数进行不同的分组，得到的总数相同。
- 能选出先相加的两个数，使计算更简便。
- Solve 2 + 6 + 4 by first adding 6 + 4 = 10, then 2 + 10 = 12
- Explain that grouping addends differently gives the same total
- Choose which two numbers to add first to make the calculation easier
评估问题 / Assessment
如果{{name}}要计算 3 + 7 + 6，能发现先算 3 + 7 凑成 10 更简便，而不是一直从左往右算吗？
If {{name}} needs to add 3 + 7 + 6, can they spot that adding 3 and 7 first (to make 10) is easier — rather than always working left to right?