(i) Multiples of 2 are 2, 4, 6, 8, 10, 12, 14, ...
Multiples of 3 are 3, 6, 9, 12, 15, 18, 21, ...
∴ 12 is a common multiple of 2 and 3.
(ii) Multiples of 3 are 3, 6, 9, 12, 15, 18, ...
Multiples of 5 are 5, 10, 15, 20, 25, ...
∴ 15 is a common multiple of 3 and 5.
(iii) Multiples of 4 are 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, ...
Multiples of 5 are 5, 10, 15, 20, 25, 30, 35, 40, 45, ...
∴ 20 and 40 are common multiples of 4 and 5.
(iv) Multiples of 5 are 5, 10, 15 20, 25, 30, 35, 40, ...
Multiples of 7 are 7, 14, 21, 28, 35, 42, ...
∴ 35 is a common multiple of 5 and 7.