Topic 7 Percentages With Answer Key - Math Quest 7 Page 10
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40number and algebra
WOrKed eXamPle 7
WOrKed eXamPle 7
WOrKed eXamPle 7
A survey showed that 3 out of 15 locals rated the Australian Grand Prix in Albert
Park as their favourite spectator sport. What percentage is this?
THInK
WrITe
Write the information as a fraction by making the
1
20
3
3
100
=
×
%
numerator the number of people who rated the
15
1
3
15
Grand Prix as their favourite spectator sport and
the denominator the total number of people.
100
Change to a percentage by multiplying by
and
2
1
including the % sign.
Cancel or simplify as appropriate.
3
1
3
20
=
×
%
1
1
3
Multiply the numerators and then multiply the
4
20
=
%
1
denominators.
= 20%
Simplify.
5
6
Answer the question by writing a sentence.
20% of the locals surveyed
rated the Australian Grand
Prix in Albert Park as their
favourite spectator sport.
Changing decimals to percentages
• To change a decimal to a percentage, multiply the decimal by 100 by moving the
decimal point two spaces to the right, and add a % sign.
WOrKed eXamPle 8
WOrKed eXamPle 8
WOrKed eXamPle 8
Change each of the following decimals to percentages.
0.38
0.275
4.2
a
b
c
THInK
WrITe
0.38 = 0.38 × 100%
Write the decimal, multiply it by 100 (that
a
1
a
is, move the decimal point two places to
the right) and include the % sign.
= 38%
Write the answer.
2
0.275 = 0.275 × 100%
Write the decimal, multiply it by 100 (that
b
1
b
is, move the decimal point two places to
the right) and include the % sign.
= 27.5%
2
Write the answer.
4.2 = 4.2 × 100%
c
1
Write the decimal, multiply it by 100, fi ll the
c
blanks with zeros and include the % sign.
= 420%
2
Write the answer.
Topic 7 • Percentages
253
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