Section 3.7 – Relating Fractions, Decimals and Percents
Percent - number out of 100. It is the numerator of a fraction which has
a denominator of 100
We know that 0.63 =
Therefore it is 63%.
Example 1: Write the following percents as fractions out of 100 (reduce if possible)
and as decimals.
a) 5% =
÷5 =
b) 17% =
= 0.17
c) 50% =
÷50 =
d)
=
= 0.333
= 0.05
Example 2: Write each as a fraction over 100 and then as a percent.
a)
x 10 =
= 20%
b)
x2=
= 34%
c)
x4=
= 80%
d)
=
e)
f)
= 85%
=
0.35 =
= 17.7%
= 35%
Let’s consider benchmarks
100% - is all so 1
75% - is three quarters (3/4) so 0.75
50% - is half (1/2) so 0.5
25% - is a quarter (1/4) so 0.25
Example 3: Why is 70% not a good estimate for 35 out of 80.
is 50% so
is less than 50%. So it does not make sense to be 70%.
Example 4: Explain how you would estimate the percentage when a test score is 26
marks out of 55.
Its approximately 25 out of 50 which is 50%
Example 5: Determine the percent of a book that is left to read if the class has read
60 out of 150 pages. Explain your thinking.
Read
= 0.4 = 40%
So full book is 100% - 40% = 60% left to read
Example 6: Change each fraction to a percent then a decimal
Fraction
a)
x2 =
Percent
x 10=
Decimal
40%
0.40
b)
x4 =
80%
0.80
c)
x2 =
12%
0.12
d)
x5 =
35%
0.35
75%
0.75
e) x 25 =
Example 7: Place each number in question 6 on number line
0%
12%
25%
35%
40%
50%
75%
80%
100%