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List the first five common multiples of 2, 3 and 4.

CHAPTER
2 Multiples of 2 : 2, 4, 6, 8, 10, 12 , 14, … Determine the first common
multiple of 2, 3 and 4. Then
Multiples of 3 : 3, 6, 9, 12 , 15, … determine the multiples of
the first common multiple.
Multiples of 4 : 4, 8, 12 , 16, …
The first common multiple of 2, 3 and 4 is 12.
Thus, the first five common multiples of 2, 3 and 4 are 12, 24, 36, 48 and 60.

Self Practice 2.2a

1. Determine whether each of the following numbers is a common multiple of the list
of numbers in the brackets.
(a) 72 (9, 12) (b) 168 (2, 9) (c) 360 (4, 6, 24)
(d) 2 250 (2, 5, 9) (e) 9 720 (4, 5, 10, 20) (f) 16 416 (6, 9, 12, 24, 36)

2. List the first five common multiples of each of the following lists of numbers.
(Use an electronic spreadsheet to help you)
(a) 2, 5 (b) 3, 5 (c) 18, 22 (d) 3, 5, 8
(e) 2, 3, 6, 8 (f) 4, 8, 12, 15 (g) 6, 15, 20, 24 (h) 4, 9, 12, 15, 18

What is lowest common multiple (LCM)? LEARNING
STANDARDS
We have learnt that the common multiples of 6 and 8 are Determine the LCM

24, 48, 72, 96, ... . Among these common multiples, the first of two and three
common multiple, 24, is the least number. The number 24 is whole numbers.
known as the lowest common multiple (LCM) of 6 and 8.

LCM can be determined by using the methods of
• listing the common multiples
• repeated division Explain how you would
1
1
• prime factorisation use LCM to solve + .
6 8
11
Determine the lowest common multiple of
(a) 2 and 3 (b) 3, 6 and 9 (c) 3, 8 and 12

(a) Method of listing the common multiples
Multiples of 2 : 2, 4, 6 , 8, 10, …
Choose the lowest
Multiples of 3 : 3, 6 , 9, 12, … common multiple.
The lowest common multiple is 6.

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Chapter 2

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