Factors, Powers And Standard Form Worksheet Page 3
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21E
5
Mince pies come in boxes of 8. Beth has bought some boxes of mince
pies for a party. Beth counts the mince pies and says there are 130.
Tom counts them and says there are only 128.
Who is correct? Give a reason for your answer.
6
Nisha has written down a multiple of 8. She says that if she adds a
2
AO
zero to the end of her number it will still be a multiple of 8.
Is Nisha correct? Give a reason for your answer.
Lowest common multiples
The lowest common multiple (LCM) of two numbers is the
The lowest common
multiple is also known as
smallest number that is a multiple of both numbers.
the least common multiple.
The multiples of 3 are 3, 6, 9, 12, 15, 18, 21, 24, …
The multiples of 4 are 4, 8, 12, 16, 20, 24, …
The common multiples of 3 and 4 are 12, 24, …
Another way to fi nd LCMs is
So the lowest common multiple of 3 and 4 is 12.
covered in Section 10.5.
Example 2
C
What is the lowest common multiple of 6 and 8?
Write down the multiples of both numbers and circle the common multiples.
Multiples of 6: 6, 12, 18, 24 , 30, 36, 42, 48 , …
Multiples of 8: 8, 16, 24 , 32, 40, 48 , …
6 3 8 5 48 is defi nitely a
The common multiples are 24, 48, …
common multiple of 6 and 8
so you can stop at 48.
The lowest common multiple is 24.
Exercise 10B
D
1
a
Write down the fi rst ten multiples of 6.
LCM stands for lowest
b
Write down the fi rst ten multiples of 9.
common multiple.
c
What is the LCM of 6 and 9?
2
Write down two common multiples of
a
2 and 3
b
4 and 5
c
2 and 10
d
9 and 3
C
3
Work out the lowest common multiple of
a
5 and 6
b
8 and 10
c
2 and 5
d
10 and 15
e
12 and 15
f
20 and 30
4
Shazia says that you can fi nd the LCM of two numbers by multiplying them
together. Give an example to show that Shazia is wrong.
160
Factors, powers and standard form
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