① Multiples, factors & primes
List multiples, find all factors of a number, and identify prime numbers.
② Highest Common Factor (HCF)
Find the largest factor shared by two numbers. Useful for simplifying fractions and dividing things equally.
③ Lowest Common Multiple (LCM)
Find the smallest multiple shared by two numbers. Useful for adding fractions and solving timing problems.
④ Mixed — HCF, LCM & prime factors
Mixed questions including prime factor decomposition. You choose which technique is needed.
Key definitions
Multiple: result of multiplying a number by a positive integer. Multiples of 6: 6, 12, 18, 24…
Factor: divides exactly into a number. Factors of 12: 1, 2, 3, 4, 6, 12.
HCF: largest factor shared by two numbers. HCF of 12 and 18 = 6.
LCM: smallest multiple shared by two numbers. LCM of 4 and 6 = 12.
Prime: exactly two factors — 1 and itself. First primes: 2, 3, 5, 7, 11, 13, 17, 19…