PERCENTAGE.
Per cent means ‘out of 100’. Writing an amount as a percentage means writing it as a number out of 100.
A percentage is a fraction whose denominator is 100. Percentages are used frequently in Mathematics calculations.
Example
Express 20 as a percentage of 50
Solution
i) Write the amount as a fraction.
20/50
ii) Write an equivalent fraction which is ‘out of 100’ by multiplying top and bottom by the same number.
(20×2) / (50×2) =40/100
ii) Write the amount as a percentage.
40/100=40%
So 20 is 40% of 50.
Alternative method,
1) Write the amount as a fraction.
20/50
2)Divide the top number by the bottom number.
20/50= 0.4
3) Multiply 0.4 by 100% to write as a percentage.
0.4×100%=40%
So 20 is 40% of 50.
EXERCISE
Write each of the following amount as a percentage.
a) 33 out of 50
ANS
33/50
b) 3 out of 20
ANS
3/20
c) 54 out of 180
ANS
54/180
d) 200 out of 160
ANS
200/160
e) 890 out of 1000
ANS
890/1000
2) A chess club has 25 members, 12 of these members are female. Express the number of female members of the club as a percentage.
Solution
We are required to find the percentage of female members of the club.
Hence we have to find the percentage of 12 females out of 25 members of the chess club.
12/25×100%= 48%
Hence, 48% of chess club members are females.
3) There are 300 counters in a bag, 45 of which are green. Express the amount of green counters as a percentage.
Solution
We are required to find the percentage of 45 green counters out of 300 counters in a bag.
45/300×100%= 15%
Hence, 15% of counters in a bag are green.
4) Out of 24 pupils in a class, 18 walks to school
a) What Percentage of the class walk to school.
Solution
We are required to find the percentage of pupils who walk to school where by 18 pupils walk to school out of 24 pupils.
We calculate the percentage of class walk as follows
18/24×100%= 75%
Hence, 75% percentage of the pupils walk to school.
b) What percentage of the class do not walk to school.
Solution
We are required to find the percentage of pupils who do not walk to school where by 18 pupils walk to school out of 24 hence (24-18=6) do not walk to school, hence we calculate the percentage of these 6 students who do not walk to school as follows
6/24×100%= 25%
Hence, 25% percentage of the pupils do not walk to school.
5)39 out of 65 people in a book club have blonde hair. What percentage do not have blonde hair.
Solution
We are given the information that 39 people have a blonde hair in a book club which has a total of 65 people hence (65-39=26) do not have blonde hair in this book club.
Therefore we need to find the percentage of these 26 people who do not have blonde hair.
26/65×100%=40%
Hence,40% of people do not have blonde hair.
6) Write each of the following as a percentage.
a) 116.6 out of 212
Solution
116.6/212×100%=55%
b) 697.15 out of 382
Solution
697.15/382×100%=182.5%
c) 17.92 out of 512
Solution
17.92/512×100%=3.5%
d) 226.8 out of 210
Solution
226.8/210×100%=108%
e) 47.25 out of 126
Solution
47.25/126×100%=37.5%
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