Remarkable / Worksheets / Grade 7 Maths / Factors, primes, HCF and LCM
A one-page CAPS Grade 7 Maths poster on factors, primes, HCF and LCM (Numbers), with the key ideas, key words and a tip to remember.
Factors divide into a number exactly. Multiples are the answers in its times table.
Factors of 28: 1, 2, 4, 7, 14, 28
Multiples of 6: 6, 12, 18, 24, 30
Break a number into primes with a factor tree. Write repeated primes with exponents.
150 = 2 × 75 = 2 × 3 × 25
150 = 2 × 3 × 5 × 5 = 2 × 3 × 5²
The biggest number that divides into both numbers. List the factors, or multiply the common prime factors.
Factors of 18: 1, 2, 3, 6, 9, 18
Factors of 27: 1, 3, 9, 27
The HCF of 18 and 27 is 9.
The smallest number that is a multiple of both numbers. List the multiples of the bigger number until one fits.
Multiples of 10: 10, 20
20 is a multiple of 4, so the LCM of 4 and 10 is 20.
HCF: take the common primes with the smaller exponents. LCM: take all the primes with the bigger exponents.
20 = 2² × 5 and 50 = 2 × 5²
HCF = 2 × 5 = 10
LCM = 2² × 5² = 100
Learners can practise this topic for free with a short quiz and flashcards, with no sign-up. Open the Factors, primes, HCF and LCM revision.