Numeracy Worksheet - Castlebrae Community High School - 2012 Page 21
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47FHS Numeracy
Estimation: Rounding
contents page
The same principle applies when rounding decimal numbers.
Example 1
Round 1.5739 to 1 decimal places (1.d.p.)
Level 3
st
The 1
number after the decimal point (5) is the position
of our place value. The rounded number lies between 1.5 and 1.6
nd
The 2
number after the decimal point is a 7. (this is the “check digit”). 7
means round up.
1.5739 = 1.6 (1.d.p.)
Example 2
Round 6.4721 to 2 decimal places (2.d.p.)
Level 3
nd
The 2
number after the decimal point (7) is the position
of our place value. The rounded number lies between 6.47 and 6.48
rd
The 3
number after the decimal point is a 2. (this is the “check digit”). 2
means round down.
6.4721 = 6.47 (2 d.p.)
Example 3
Round 19.49631 to 2 decimal places (2.d.p.)
Level 3
19.49631 = 19.50 (2.d.p.)
The number lies between 19.49 and 19.50.
6 to the right means we round up.
We must include the 0 at the end as we
require 2 numbers after the point.
0, 1, 2, 3, 4
lower
Some students need a bit more visual help.
5, 6, 7, 8, 9
upper
You could also use a mini number line.
Example 1
1. 5 7 3 9 = 1.6 (1.d.p.)
1.5
1.6
7 upper
Level 3
Example 2
6. 4 7 2 1 = 6.47 (2 d.p.)
6.47
2 lower
6.48
Level 3
21
L Watson 2012
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