Addition and subtraction (I)
Adding two-digit numbers, with carrying, and subtracting them without borrowing, with answers up to 100; lining up units under units and tens under tens in column form; adding three numbers, making a ten first to help; checking a subtraction by adding; and simple word problems.
Key words
| Chinese | English |
|---|---|
| 直式 | column form |
| 進位 | carry |
| 驗算 | check (an answer) |
| 應用題 | word problem |
The 13 short lessons and the chapter test
Lessons are in Chinese for now.
- 整十的加減
- 兩位數加法
- 直式要對位
- 進位加法
- 直式加法
- 兩位數減法
- 驗算
- 找出未知數
- 直式填數字
- 三個數相加
- 湊整十
- 應用題
- 三個數的應用題
- 章節測驗 (chapter test)
Sample questions (in Chinese)
Question 1計算。
59 + 16 =
Answer and explanation
答案：59 + 16 = 75
為甚麼？個位：9 + 6 = 15，寫 5，向十位進 1；十位：5 + 1 + 1 = 7。所以 59 + 16 = 75。
Question 2計算。
48 − 44 =
Answer and explanation
答案：48 − 44 = 4
為甚麼？個位：8 − 4 = 4；十位：4 − 4 = 0。所以 48 − 44 = 4。
Question 3用直式計算。
27 + 12 =
Answer and explanation
答案：27 + 12 = 39
為甚麼？直式要對位，由個位開始計算。個位：7 + 2 = 9；十位：2 + 1 = 3。所以 27 + 12 = 39。
Question 4由左至右計算。
32 + 3 + 29 =
Answer and explanation
答案：32 + 3 + 29 = 64
為甚麼？三個數相加，由左至右計算：32 + 3 = 35，35 + 29 = 64。
Based on learning unit 1N4 of the Education Bureau’s Primary Mathematics Curriculum (2017).