First let’s remind ourselves about **order of operations**. If you have a calculation like 2+7×3 or (2-7)x3, do you do the calculations from left to right? If not, how should you do them?

**Exercise**

Let’s complete the short exercises “exercise 12” and “exercise 13” on page 88 of the core textbook:

The answers are below:

**Factors and multiples**

We need to remember what the **factors **of a number are and what the **multiples **of a number are. We also need a reliable method for finding the **highest common factor** and the **lowest common multiple** of a number. Rewriting a number as a product of its prime factors can help us a lot in tackling problems involving factors an d multiples. Let’s try doing this for several numbers and then try finding the **HCF** and **LCM** of various pairs of numbers.

**Exercise**

Let’s complete exercise 14 on pages 89 to 91 of the core textbook:

The answers are below:

**Irrational numbers**

Do you know what an **irrational number **is? What does the word **irrational **mean in mathematical terms? Could you identify a rational number between 3 and 4?

**Exercise**

Let’s complete exercise 15 on pages 91 and 92 of the core textbook:

The answers are below: