Learning Log #8
Scale Factor
5m
B
20m
64m
A
A
A
256m
Learning Log #8 - Scale Factor
•Always start by asking yourself “which side corresponds to which side?”
This side
corresponds to
this side.
Angles
5m
B
20m
64m
A
If two images
are similar,
the angles
remain the
same!
A
A
256m
And you need to ask yourself, what multiplied by 5 makes 20? Or you could
simply do 20 ÷ 5 = 4. 4 is our scale factor from B to A because 5 * 4 = 20m.
The reverse, A to B, 20 * ¼ = 5. We get ¼ by using the reciprocal of 4.
Remember, Scale Factor is always expressed as multiplication not division.
Scale Factor from
A to B is 1/6
because
30m * 1/6 = 5m
24m *1/6 is 4m
Learning Log #8
Scale Factor
“How do they compare?”
SF & Perimeter
Perimeter of B is 12m
Scale Factor B to A is 6
P * SF = Area of A
12m * 6 = 72m
B to A is 6
because
72m is the perimeter of A
* 1/6
5m * 6 = 30m
4m * 6 = 24m
B to A the Perimeter is 6
times larger.
4m
30m
B
24m
3m
A
A
5m
SF & Area
Area of B is 6m²
A
Scale Factor B to
A is 6 & 6² = 36
18m
Area * SF² = Area
SF & Side Lengths
The side-lengths
from B to A are 6
times larger.
*6
of
A
36*6m² = 216m²
B to A the area is
36 times larger.
Scale Factor: Area & Perimeter
Perimeter
1st P * SF = 2nd P
Area
1st A * SF² = 2nd A
Variables Defined
Variables Defined
P = perimeter
1st P = 1st perimeter
2nd P = 2ndperimeter
SF = Scale Factor
A = Area
1st A = 1st Area
2nd P = 2nd Area
SF = Scale Factor
Angles
And remember, if two images are similar the angles remain the
same!