Exercise 1.3
More about prime numbers
1 Copy and complete these factor trees. b c a 88 135 8
11
9
15
260
26
10
2 a Draw two different factor trees for 80. b Write 80 as a product of primes. 3 Write down each number. b 24 × 33 a 2 × 32 × 52
c 22 × 112
4 84 = 22 × 3 × 7 and 90 = 2 × 32 × 5 a Write the HCF of 84 and 90 as a product of primes. b Write the LCM of 84 and 90 as a product of primes. 5 a Write each number as a product of primes. i 120 ii 160 b Find the LCM of 120 and 160. c Find the HCF of 120 and 160. 6 a Find the HCF of 84 and 96. b Find the LCM of 84 and 96. 7 a Find the HCF of 104 and 156. b Find the LCM of 104 and 156. 1000 = 23 × 53 8 10 = 2 × 5 100 = 22 × 52 Write 10 000 as a product of primes. 9
I am thinking of two prime numbers.
I can tell you their HCF.
I can tell you how to find their LCM.
a How can Sasha do that? b What will Razi tell Jake? 10 a Write 81 as a product of primes. b Write 154 as a product of primes. c Explain why the HCF of 81 and 154 must be 1.
1
Integers, powers and roots
9