Four arithmetic operations (I)
Brackets, and working out what is inside them first; mixed addition and subtraction of three numbers up to four digits; multiplying before adding or subtracting; recognising relations such as a × (b + c) = a × b + a × c (without changing one side into the other); word problems that combine "how many more" and "altogether"; and estimating.
Key words
| Chinese | English |
|---|---|
| 圓括號 | brackets |
| 加減混合 | mixed addition and subtraction |
| 先乘後加減 | multiply before adding and subtracting |
| 總和 | total |
| 估算 | estimate |
The 14 short lessons and the chapter test
Lessons are in Chinese for now.
- 圓括號
- 加減混合
- 先乘後加減
- 乘加和乘減
- 四個數的計算
- 加上圓括號
- 比較算式
- 答案相同的算式
- 找出錯處
- 找出未知數
- 比多少和總和
- 購物
- 兩步應用題
- 估算
- 章節測驗 (chapter test)
Sample questions (in Chinese)
Question 1計算。
66 − (28 + 21) =
Answer and explanation
答案：66 − (28 + 21) = 17
為甚麼？有圓括號，先算括號內：28 + 21 = 49；再算 66 − 49 = 17。
Question 2計算。
3983 − 2447 + 1541 =
Answer and explanation
答案：3983 − 2447 + 1541 = 3077
為甚麼？只有加和減，由左至右計算：先算 3983 − 2447 = 1536，再算 1536 + 1541 = 3077。
Question 3計算。
3 × 3 + 57 =
Answer and explanation
答案：3 × 3 + 57 = 66
為甚麼？先乘後加減：3 × 3 = 9；再算 9 + 57 = 66。
Question 4哪一個算式的答案是 72？
- (6 + 2) × 9
- 6 + 2 × 9
- 6 + (2 × 9)
Answer and explanation
答案：A．(6 + 2) × 9
為甚麼？有圓括號先算括號內：(6 + 2) × 9 = 72。另外兩個算式都是先乘後加，答案是 24。
Based on learning unit 3N4 of the Education Bureau’s Primary Mathematics Curriculum (2017).