熟练进行20以内的加减法

能运用心算策略熟练完成20以内的加法和减法，并能熟记所有一位数加一位数的和。

Fluently add and subtract within 20 using mental strategies; know from memory all sums of two one-digit numbers

学习证据 / Evidence

• 能在3秒内答出任意一道一位数加法题
• 能凭记忆说出20以内的减法算式结果（例如15 − 8 = 7）
• 能利用已知的加法算式快速推出相应的减法算式

• Answer any single-digit addition fact within 3 seconds
• Recall subtraction facts within 20 from memory (e.g. 15 − 8 = 7)
• Use known addition facts to derive related subtraction facts rapidly

评估问题 / Assessment

{{name}}能不用数数或思考超过一秒，就立刻说出所有一位数加法算式的结果吗——比如“7 + 8 = 15”？

Can {{name}} instantly recall all the single-digit addition facts — like '7 + 8 = 15' — without needing to count or think for more than a second?