# 1.7 Multiplication

## Multiplication by 10, 100 and 1 000

### ×10

To multiply a whole number by 10, we write the number then add one zero on the end. For example:

2 × 10 = 20 (2 × 1 = 2, then add a zero)

6 × 10 = 6**0**

10 × 10 = 1**00**

### ×100

When we multiply a whole number by 100, we add two zeros to the end of the number. For example:

3 × 100 = 3**00**

25 × 100 = 2 5**00**

60 × 100 = 6 0**00**

### ×1 000

When we multiply a whole number by 1 000, we add three zeros to the end of the number. For example:

4 × 1 000 = 4 **000**

32 × 1 000 = 32 **000**

50 × 1 000 = 50 **000**

Now try the following activity.

### Activity 8: Multiplying whole numbers by 10, 100 and 1 000

Now try the following:

- 7 × 10
- 32 × 10
- 120 × 10
- 8 × 100
- 21 × 100
- 520 × 100
- 3 × 1 000
- 12 × 1 000
- 45 × 1 000
- Pens cost 31 pence each. How much would it cost for a pack of ten pens?
- A supermarket buys boxes of cereal in batches of 100. If they buy 19 batches, how many boxes is this?
- Seven people win £1 000 each on the lottery. How much money is this altogether?

#### Answer

- 70
- 320
- 1 200
- 800
- 2 100
- 52 000
- 3 000
- 12 000
- 45 000
- 310 pence (or £3.10)
- 1 900 boxes of cereal
- £7 000