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 = 60
10 × 10 = 100
×100
When we multiply a whole number by 100, we add two zeros to the end of the number. For example:
3 × 100 = 300
25 × 100 = 2 500
60 × 100 = 6 000
×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