Decimal Numbers Worksheet Page 3
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1
2
3
4o
D ecim al N um bers - 3
E SO
3
3. Multiply (A) by 100 (because there are two recurring figures):
1000x = 2563.636363 . . .
(B)
4. Subtract B A:
1000x = 2563.636363 . . .
10x =
25.636363 . . .
990x = 2538
2538
141
5. Divide by 990 and simplify: x =
=
990
55
Exercises - Set B
1.
Write as decimals, and state in each case whether they are terminating or recurring decimals:
7
2
5
4
44
a)
b)
c)
d)
e)
50
125
9
11
7
87
11
33
3
3
f)
g)
h)
i)
j)
60
3
22
20
5
2.
Write as a fraction in its lowest terms:
0. ˙ 7
0. ˙ 5 ˙ 4
0.1 ˙ 2
a)
0.15
b)
0.046
c)
d)
e)
3.40 ˙ 7
0. ˙ 30 ˙ 5
0. ˙ 4 ˙ 8
4. ˙ 2
1. ˙ 2 ˙ 7
f)
g)
h)
i)
j)
3.
Calculate. Firstly you must express decimals as fractions:
2
1
3
3
0. ˙ 4 ˙ 6
· 2. ˙ 4
0. ˙ 1 ˙ 4
a)
+ 3.6
b)
c)
5
2 ·
5
3
5
5
1
4.
Shula says, “I used my calculator to change
to a decimal, and I got the answer 0.07692308.
13
There is no repeating pattern, so the decimal does not recur.” Explain why Shula is wrong.
3. Approximation and rounding
Rounding a number is a way of writing it approximately. Sometimes we don’t need to write all the
figures in a number, as an approximate one will do.
For example: for a population of 27 653 the number is large and will change daily. It is better to
round up and say 28 000.
When rounding numbers to a given degree of accuracy, look at the next digit:
• If it is 5 or more then we have to round up , that is, increase the previous digit by one.
• Otherwise we round down , that is, leave the previous digit unchanged.
For example, to round 7.365 to 2 decimal places, look at the thousandths digit: 7.365.
The thousandths digit is 5, so we round up to 7.37: 7.365≈7.37 (to 2 decimal places).
Numbers can be rounded:
D pto. M atemáticas. IES Jovellanos. 2011
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