A factor divides a number exactly. The factors of 12 are 1, 2, 3, 4, 6 and 12, and they come in pairs that multiply to 12: 1 × 12, 2 × 6 and 3 × 4. A multiple is in a number's times table: multiples of 4 are 4, 8, 12, 16 and so on.
A prime number has exactly two factors, 1 and itself, like 2, 3, 5, 7, 11 and 13. A composite number has more than two factors, like 9 or 15. The number 1 is neither prime nor composite.
Worked example
List the factor pairs of 18.
- Try 1, 2, 3 and so on: 1 × 18, 2 × 9, 3 × 6.
- 4 and 5 do not divide 18. After 3 × 6 the pairs repeat.
Answer:1 × 18, 2 × 9 and 3 × 6
Key words
- factor
- a number that divides exactly into another
- multiple
- the result of multiplying by a whole number
- prime
- has exactly two factors
- composite
- has more than two factors
Practise this
New questions every time.
Common Core-referenced: 4.OA.B.4