Factor (ước số) và Multiples (bội số) là một trong những chủ đề có trong chương trình Cambridge Primary (grade 5), nhưng là kiến thức mới với HS lớp 5 Việt Nam. Các câu hỏi trong bài này là những câu hỏi ở mức độ cơ bản, được trích từ chương trình toán Singapore online nổi tiếng tên là Koobits.

**Definition: **

Factors and multiples are **different** things. But they both involve **multiplication**:

- Factors are what we can multiply to get the number
- Multiples are what we get
**after**multiplying the number by an integer (not a fraction).

Factors:

- 1 × 6 = 6, so
**1**and**6**are factors of 6 - 2 × 3 = 6, so
**2**and**3**are factors of 6

Multiples:

- 0 × 6 = 0, so
**0**is a multiple of 6 - 1 × 6 = 6, so
**6**is a multiple of 6 - 2 × 6 = 12, so
**12**is a multiple of 6 - and so on

**Is 85 a multiple of 4?**

- Yes
- No

**Is 4 a common factor of 24 and 96?**

- Yes
- No

**Determine if 6 is a factor of 32?**

- Yes
- No

**The first five multiples of 9 are 9, , 27, 36, .**

**The first five multiples of 5 are , 10, , 20, 25.**

**What is the fourth multiple of 7?: .**

**What is the third multiple of 7?: .**

**Determine if 5 is a factor of 45?**

- Yes
- No

**Is 9 a common factor of 81 and 108?**

- Yes
- No

**What is the fifth multiple of 6?: **

**Miko and her sister's age are the first two multiples of 5 respectively. What is their total age?:** **years old**.

**What is the second common multiple of 4 and 5?:** .

**What is 4 multiplied by the first common multiple of 3 and 5?:** .

**The number of seashells that Minnie has is the first common multiple of 8 and 10. Minnie's sister has 5 times as many seashells as Minnie. How many seashells does Minnie's sister have?:** **seashells.**

**The number of seashells that Cheryl has is the first multiple of 8. The number of seashells that Tiffany has is the second multiple of 8. The number of seashells that Elise has is the third multiple of 8. How many seashells do the 3 girls have altogether?:** .

**What is 3 multiplied by the first common multiple of 2 and 4?:** .

**What is 3 multiplied by the first common multiple of 2 and 6?:** .

**What is 6 multiplied by the first common multiple of 3 and 8?:** .

**What is 6 multiplied by the first common multiple of 5 and 6?:** .

**What is the first common multiple of 3 and 4?**

*(Write your answer in numerals):* .