COMPARATIVE PIE CHARTS

1
COMPARATIVE PIE CHARTS
If we want to make a similar pie chart about the
flavours of ice creams liked by a whole year
group of 120 should it be the same size?
strawberry
vanilla
BUT HOW BIG?
blueberry
This is a pie chart representing the flavour of
ice creams liked by a class of 30 children
2
What would happen to the area if we multiplied
the side length by 3?
We are going to make this 3 x 3 square bigger by
making the sides twice as long
NOT JUST ONE SIDE WE MUST END UP WITH A
SQUARE!!!
So how many times bgger in AREA is the large
square when compared to the small one?
3
Lengths x 4
20cm
5cm
Area 25 cm2
Does it matter what size square we start with?
Area 400 cm2
Areas x 16
Areas x 100
Length x 10
50cm
Area 2500 cm2
4
So we can summarise
Fill out the table below
Side length of small square Side length of large square Area of small square Area of large square
8 16
15 25
k 5k h
w 100t 10000t
64
256
125
5
25h
10w
Length scale factor Area scale factor
6
49
k2
36
7
k
5
So now to the pie charts
Area scale factor 9
Area 180cm2
Area 20 cm2
So how many times longer is the radius?
Length scale factor 3
6
So now to the pie charts
Area scale factor 16
Pie chart to represent 320 people
Pie chart to represent 20 people
So if we make the radius of the small circle 6cm
how long is the radius of the large circle?
Length scale factor 4
So the radius of the large circle would be 4 x 6
24 cm
7
So now to the pie charts
Area scale factor 10
Pie chart to represent 400 people
Pie chart to represent 40 people
So if we make the radius of the small circle 3cm
how long is the radius of the large circle?
Length scale factor v10
So the radius of the large circle would be v10 x
3 3 v10 cm
8
So back to the original problem
9
COMPARATIVE PIE CHARTS
If we want to make a similar pie chart about the
flavours of ice creams liked by a whole year
group of 120 should it be the same size?
strawberry
vanilla
The radius of the pie chart for 30 children is
5cm, what is the radius for the pie chart for 120
children?
blueberry
This is a pie chart representing the flavour of
ice creams liked by a class of 30 children
10 cm
10
Work sheet for comparative pie charts
Squares
Side length of small square Side length of large square Area of small square Area of large square
8 16
15 25
k 5k h
w 100t 10000t
Generally
Length scale factor Area scale factor
6
49
k2
Pie Charts
Total number in pie chart one Total number in pie chart two Area scale factor Length scale factor Radius of pie chart one Radius of pie chart two
20 320 6
40 400 3
30 120 5
1200 4 6
2.6 million 5.23million 10
16 9 4.5
11.2 thousand 3.8 thousand 5