Write down all the common factors of 18 and 30.
Need a hint?
Write the full factor list for 18 first, then check each factor to see whether it also divides 30 exactly.
Worked answer
- List the factors of 18: 1, 2, 3, 6, 9, 18.
- List the factors of 30: 1, 2, 3, 5, 6, 10, 15, 30.
- Pick out the numbers that appear in both lists: 1, 2, 3, 6.
Answer: 1, 2, 3, 6
The mistake this question tests
Habit
Factors and multiples (HCF, LCM)
Pupils often list the factors of only one number, or stop too early and miss 1, so the common list comes out wrong.
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