Percentages

1
Percentages
Objectives D Grade Express one quantity as a
percentage of another
Prior knowledge
Understand how to
Convert fractions to equivalent fractions
Convert fractions to decimals
Convert decimals to percentages
2
Percentages
What is a percentage?
percent
per
cent
out of
hundred
So we can think of percentages also as fractions
with a denominator of 100
This helps us to understand that finding a
percentage of a quantity is the same as finding a
fraction of a quantity
e.g.
65 percent
65
65
per
0
0
cent
3
Percentages
Expressing one quantity as a percentage of
another
Compare one quantity with the other.
e.g. compare 20 with 25
20
Write
compare with
25
Write as an equivalent fraction with the
denomination 100

This is now 80
because 80 is the same as 80 100
4
Percentages
Sometimes you might need to have an intermediate
equivalent fraction
e.g. compare 4 with 40
4
Write
compare with
40
Simplify as an equivalent fraction

Now write as an equivalent fraction with the
denominator of 100

This is now 10
because 10 is the same as 10 100
5
Percentages
Now do these 1. Write 4 as a percentage of
20 2. Write 50 as a percentage of
200 3. Write 14 as a percentage of
28 4. Write 4 as a percentage of 25 5. Write
18 as a percentage of 45
6
Percentages
Harder percentages of quantities can be found
using a calculator.
24
can be read as
compare with
34
Convert from a fraction to a decimal
Using a calculator
24 34 0.7059
Convert from a decimal to a percentage
0.7059 100 70.59
70.59
7
Percentages
Now do these 1. Write 3 as a percentage of
72 2. Write 42 as a percentage of
76 3. Write 45 as a percentage of
135 4. Write 37 as a percentage of
52 5. Write 92 as a percentage of 56