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AQA GCSE · Question 04.1 · Number
Write down all the factors of 20.
Write down all the factors of 20.
How to approach this question
Factors are numbers that divide exactly into another number. To find all the factors of 20, it's best to work in pairs.
1. Start with 1: 1 × 20 = 20. So, 1 and 20 are factors.
2. Try 2: 2 × 10 = 20. So, 2 and 10 are factors.
3. Try 3: 20 is not divisible by 3.
4. Try 4: 4 × 5 = 20. So, 4 and 5 are factors.
5. The next number to try is 5, which we already have. So we have found all the pairs.
List them in order: 1, 2, 4, 5, 10, 20.
Full Answer
A factor of a number is an integer that divides into that number without leaving a remainder. A systematic way to find all factors of 20 is to check each integer starting from 1.
- 20 ÷ 1 = 20 (so 1 and 20 are factors)
- 20 ÷ 2 = 10 (so 2 and 10 are factors)
- 20 ÷ 3 = 6 remainder 2 (so 3 is not a factor)
- 20 ÷ 4 = 5 (so 4 and 5 are factors)
Once the numbers you are checking meet in the middle (e.g., after 4 comes 5, which is already listed), you have found all the factors.
The factors of 20 are 1, 2, 4, 5, 10, 20.
Common mistakes
✗ Forgetting some factors, especially 1 and the number itself (20).\n✗ Listing multiples instead of factors (e.g., 20, 40, 60...).
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