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(b) Method of repeated division
1. Divide the numbers repeatedly by a divisor that can
3 3 , 6 , 9 divide completely at least one of the numbers.
2. Numbers that cannot be divided completely by CHAPTER
2 1 , 2 , 3 the selected divisor are brought down for
3 1 , 1 , 3 subsequent divisions.
3. Division is continued until all the quotients become 1. 2
1 , 1 , 1

Thus, LCM of 3, 6 and 9 is 3 × 2 × 3 = 18.

(c) Method of prime factorisation
3 = 3
8 = 2 × 2 × 2 Find the prime factorisation of
12 = 2 × 2 × 3 each of the given numbers.
2 × 2 × 2 × 3

Thus, LCM of 3, 8 and 12 is 2 × 2 × 2 × 3 = 24.

3, 8, 12 1. Identify the greatest number.
2. List the multiples of the greatest number.
12, 24, 36, … 3. Determine the lowest multiple that can be divided
completely by all the other given numbers.
24 can be divided
completely by 3 and 8.

Thus, LCM of 3, 8 and 12 is 24.

Self Practice 2.2b

1. By using a suitable method, find the lowest common multiple of each of the
following lists of numbers.
(a) 16, 18 (b) 10, 15 (c) 6, 8 (d) 18, 60
(e) 6, 15, 18 (f) 8, 14, 32 (g) 9, 12, 21 (h) 4, 15, 60

How do you solve problems?
LEARNING
STANDARDS
Solve problems
Canned coffee is sold in 6 cans per box and canned tea is sold involving LCM.
in 9 cans per box. Ainun wishes to buy the same number of
canned coffee and canned tea for her sister’s birthday party.
What is the minimum number of boxes of each type of canned
drinks she needs to buy?

41
Factors and Multiples

02 TB Math F1.indd 41 11/10/16 12:08 PM