20以內不進位不退位加減
在組裝機械人的過程中，小朋友練習20以內「不進位加法」與「不退位減法」，例如 14+3、17-5。這類題目真正的學習重點是位值觀念（place value）：「十幾」就是1個十加幾個一，計算時個位對個位，不用煩惱進位退位 — 先把位值看通透。
While assembling the robot, children practise no-carry addition and no-borrow subtraction within 20, such as 14+3 and 17−5. The real learning goal is place value: "teen" numbers are one ten plus some ones, so ones line up with ones and there is no carrying or borrowing to worry about — place value comes first.
跟小朋友強調：「14是1個十和4個一。」計算 14+3 時問他：「加的是十位還是個位？」幫他建立「個位加個位」的規律感，之後學進位加法時，他才會真正明白為什麼要「過十」。
Emphasise: "14 is one ten and four ones." When solving 14+3, ask: "Are we adding to the tens or the ones?" Building the "ones add to ones" habit now means carrying will genuinely make sense later.
把日常見到的數量拆開來說：「13粒提子 = 10粒 + 3粒」。逛超市、砌積木都可以玩數字分拆，位值概念是小二學直式計算的重要根基。
Split everyday quantities out loud: "13 grapes = 10 + 3." Supermarket trips and block building are all chances to decompose numbers — place value is the foundation of the column arithmetic taught in Primary Two.