Numeracy Worksheet - Castlebrae Community High School - 2012 Page 10
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47FHS Numeracy
Multiplication
contents page
Multiplying by multiples of 10 and 100
one
To multiply by 10 you move every digit
place to the left.
two
To multiply by 100 you move every digit
places to the left.
Example 2 (a) Multiply 354 by 10
(b) Multiply 50.6 by 100
Level 2
Th
H
T
U
Th
H
T
U t
3
5
4
5
0 6
3
5
4
0
5
0
6
0 0
354 x 10 = 3540
50.6 x 100 = 5060
(c) 35 x 30
(d) 436 x 600
Level 3
To multiply by 30, multiply
To multiply by 600, multiply
by 3, then by 10.
by 6, then by 100.
35 x 3
= 105
436 x 6
= 2616
105 x 10 = 1050
2616 x 100 = 261600
So 35 x 30 = 1050
So 436 x 600 = 261600
Example 3
(a) 30 x 60
(b) 20 x 700
Level 3
3 x 10 x 6 x 10
2 x 10 x 7 x 100
= 18 x 10 x 10
= 14 x 10 x 100
= 1800
= 14000
We may also use these rules for multiplying decimal numbers.
Example 4
(a) 2.36 x 20
(b) 38.4 x 50
Level 3
2.36 x 2 = 4.72
38.4 x 5 = 192.0
4.72 x 10 = 47.2
192.0x 10 = 1920
So 2.36 x 20 = 47.2
So 38.4 x 50 = 1920
10
L Watson 2012
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