Multiples and factors
Multiples and factors, and finding the multiples and all the factors of a number; how they are related (12 is a multiple of 3, and 3 is a factor of 12); and prime and composite numbers, including why 1 is neither.
Key words
| Chinese | English |
|---|---|
| 倍數 | multiple |
| 因數 | factor |
| 質數 | prime number |
| 合數 | composite number |
The 8 short lessons and the chapter test
Lessons are in Chinese for now.
- 倍數
- 找倍數
- 因數
- 找因數
- 因數和倍數的關係
- 質數和合成數
- 找質數和愛氏篩
- 重溫
- 章節測驗 (chapter test)
Sample questions (in Chinese)
Question 16 的第 4 個倍數是多少？
Answer and explanation
答案：24
為甚麼？6 的倍數是 6 × 1、6 × 2、6 × 3……第 4 個倍數是 6 × 4 = 24。
Question 2下面哪一個是 90 的因數？
- 11
- 4
- 21
- 3
Answer and explanation
答案：D．3
為甚麼？90 ÷ 3 = 30，90 能被 3 整除，所以 3 是 90 的因數。
Question 330 共有多少個因數？
共有 個。
Answer and explanation
答案：共有 8 個。
為甚麼？一對一對地找：30 = 1 × 30 = 2 × 15 = 3 × 10 = 5 × 6，所以 30 的因數是 1、2、3、5、6、10、15、30。共有 8 個。
Question 4因為 77 ÷ 11 = 7，所以 77 是 11 的甚麼？
- 倍數
- 因數
Answer and explanation
答案：A．倍數
為甚麼？77 ÷ 11 = 7，77 能被 11 整除，所以 11 是 77 的因數，77 是 11 的倍數。
Based on learning unit 4N3 of the Education Bureau’s Primary Mathematics Curriculum (2017).