Page 16 - 新思维数学学生用书7 样章

1.3 Lowest common multiples

1.3 Lowest common multiples

In this section you will … Key words

• find out about lowest common multiples. common multiple
digit
The multiples of 4 are 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, … lowest common
The multiples of 6 are 6, 12, 18, 24, 30, 36, 42, … multiple

The common multiples of 4 and 6 are 12, 24, 36, …
The lowest common multiple (LCM) of 4 and 6 is 12. multiple

Tip

4 × 1, 4 × 2, 4 × 3,
and so on.
12 is the smallest

number that is a
multiple of both
4 and 6.

Worked example 1.6

Find the lowest common multiple of 6 and 10.

Answer

The multiples of 6 are 6, 12, 18, 24, 30, 36, …
The last digit of a multiple of 10 is 0, so 30 is a multiple of 10 and it must be the LCM
of 6 and 10.

Exercise 1.3

1 Write the first five multiples of:
a 5 b 10 c 7 d 12
2 a Write the multiples of 3 that are less than 40.

b Write the multiples of 5 that are less than 40.
c Find the common multiples of 3 and 5 that are less than 40.
3 a Find the common multiples of 4 and 3 that are less than 50.
b Complete this sentence: The common multiples of 4 and 3 are multiples of …

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