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4

List all the prime factors of 72.

1. List all the factors of 72.
CHAPTER
2 Factors of 72 are 1, 2 , 3 , 4, 6, 8, 9, 12, 18, 24, 36, 72 2. Identify the prime
numbers from the list.
Prime numbers
Thus, prime factors of 72 are 2 and 3.

5

Express 60 in the form of prime factorisation.

Method of repeated division Scan the QR Code or
visit https://youtu.
2 60 1. Perform division repeatedly be/eJLjA6uMm4g
2 30 by dividing with the smallest to learn more about
3 15 prime number. prime factorisation of
5 5 2. Division is continued until the a number.
quotient is 1.
1

Thus, 60 = 2 × 2 × 3 × 5

Method of drawing a factor tree

60 60
60 is written as the product of
2 30 two factors continuously until
4 15 or all the factors at the bottom
2 3 10 level are prime factors.

2 2 3 5 2 3 2 5

Thus, 60 = 2 × 2 × 3 × 5

Self Practice 2.1b

1. Determine whether
(a) 3, 5 and 7 are prime factors of 30.
(b) 3, 5 and 9 are prime factors of 54.

2. List all the prime factors of each of the following numbers.
(a) 36 (b) 48 (c) 58 (d) 99
3. Express each of the following numbers in the form of prime factorisation.
(a) 42 (b) 96 (c) 120 (d) 135

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Chapter 2

02 TB Math F1.indd 34 11/10/16 12:08 PM