Page 6 - 新思维数学活动用书8 样章

1 Integers

1.1 Factors, multiples and primes

Exercise 1.1 Key words

factor tree
Focus highest common

1 a Draw a factor tree for 250 that starts with 2 × 125. factor (HCF)
b Can you draw a different factor tree for 250 that starts with lowest common
2 × 125? Give a reason for your answer. multiple (LCM)
c Draw a factor tree for 250 that starts with 25 × 10. prime factor

d Write 250 as a product of its prime factors.
2 a Draw a factor tree for 300.
b Draw a different factor tree for 300.
c Write 300 as a product of prime numbers.

3 a Write as a product of prime numbers
i 6 ii 30 iii 210
b What is the next number in this sequence? Why?
4 Work out

a 2 × 3 × 7 b 2 × 3 × 7 2 c 2 × 3 × 7 3
3
3
2
2
5 a Draw a factor tree for 8712.
b Write 8712 as a product of prime numbers.
6 Write each of these numbers as a product of its prime factors.
a 96 b 97 c 98 d 99

Practice
7 Write as a product of prime numbers

a 70 b 70 2 c 70 3
8 a Write each square number as a product of its prime factors.
i 9 ii 36 iii 81
iv 144 v 225 vi 576

vii 625 viii 2401

5