Page 12 - 新思维数学学生用书8 样章

1.1 Factors, multiples and primes

3 a Draw a factor tree for 200 that starts with 10 × 20.

b Write 200 as a product of prime numbers.
c Compare your factor tree with a partner’s. Have you drawn
the same tree or different ones? Are your trees correct?
d How many different factor trees can you draw for 200 that start

with 10 × 20?
4 a Draw a factor tree for 330.
b Write 330 as a product of prime numbers.
5 Match each number to a product of prime factors.

The first one has been done for you: a and i.
a 20 i 2² × 5
b 24 ii 2 × 3 × 7
c 42 iii 2² × 3² × 5
d 50 iv 2 × 5²

e 180 v 2³ × 3
6 Work out the product of each set of prime factors.
a 3 ×× b 2 × 5 3 c 2 × 3 × 11 Tip
57
3
2
2
2
d 2 × 7 2 e 3 17 2 You can use a
×
4
7 Write each of these numbers as a product of prime factors. factor tree to
a 28 b 60 c 72 help you.
d 153 e 190 f 275
8 a Copy the table and write each number as a product of prime numbers.

Number Product of prime numbers
35 5 × 7
70
140
280

b Add more rows to the table to continue the pattern.
9 a Write 1001 as a product of prime numbers.

b Write 4004 as a product of prime numbers.
c Write 6006 as a product of prime numbers.
10 a Use a factor tree to write 132 as a product of prime numbers.
b Write 150 as a product of prime numbers.
c 132 × 150 = 19 800. Use this fact to write 19 800 as a product

of prime numbers.

11