比（10岁以上）
Ratio (age 10+)
进行包含混合运算和大数的心算，并运用拆分、补偿和基于已知事实推导等策略。
Perform mental calculations including with mixed operations and large numbers, using strategies such as partitioning, compensation, and derived facts
学习证据 / Evidence
- 将45 × 8拆分为40 × 8 + 5 × 8进行心算。
- 利用已知事实心算推导出6.5 × 4。
- 解决一个多步心算，如250 × 3 + 500，并解释所用策略。
- Mentally compute 45 × 8 by partitioning into 40 × 8 + 5 × 8
- Use known facts to derive 6.5 × 4 mentally
- Solve a multi-operation mental calculation such as 250 × 3 + 500 and explain the strategy used
评估问题 / Assessment
{{name}}能否完全在头脑中完成像 '(200 × 6) + 350 − 75' 这样的混合运算，并且记住每一步而不需写下来？
Can {{name}} work out a mixed calculation like '(200 × 6) + 350 − 75' entirely in their head — keeping track of each step without writing anything down?