Question

Consider the three numbers 4, 16 and 24. Find the sum of all the common factors? [4 marks]

Answer 1

4 = 1 × 4
= 2 × 2
= 4 x 1
Factors of 4: 1, 2, and 4 [1 mark]

16 = 1 × 16
= 2 × 8
= 4 × 4
= 8 x 2
= 16 x 1
Factors of 16: 1, 2, 4, 8 and 16 [1 mark]

24 = 1 × 24
= 2 × 12
= 3 × 8
= 4 × 6
= 6 x 4
= 8 x 3
= 12 x 2
= 24 x 1

Factors of 24: 1, 2, 3, 4, 6, 8, 12 and 24 [1 mark]

Common factors are 1, 2 and 4.
So sum = 1+2+4 = 7 [1 mark]