Find the following values without a calculator.
For 4 and 5,
- what is the first common multiple?
- what is the second common multiple?
- what is the fourth common multiple?
(a)
Multiples of 4: 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48
Multiples of 5: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50
First common multiple = 20
(a)
20 x 2 = 40
Second common multiple = 40
(a)
20 x 4 = 80
Fourth common multiple = 80
Answer(s): (a) 20; (b) 40; (c) 80