Transcript rttSS 4.1 Ratios - Quadrilaterals-3.pptx

SS 3.4 Additional Practice w/ Similar Figures
1) Teaching Target: I can use equivalent ratios to
compare corresponding sides of similar rectangles.
2) Homework: Complete notes for Inv 4.2 on p. 12 –
for the Zaption video 4.2
Warm-Up:
Ratios
describe and
compare shapes.
What is the ratio of
height to width?
8 cm
10 cm
Vocab Toolkit:
A comparison of two quantities:
the ratio of 3 to 5 means
‘3 for every 5.’
Ratios whose fraction
representations are equivalent
are called equivalent ratios.
An equation stating that
two ratios are equal.
3/5 3 to 5 3 : 5
10
8
5
3
Original
8
3
6
10 to 8
8 to 3
3 to 6
5 to 4
4
HW Review p. 12:
ratios
comparison
10 cm
fraction
8 cm
width
height
or
height
width
fractions
equivalent
scale
factor
proportion
height
width
10
8
15
X
equal
width
OR
height
1.5
X = 12
8
10
=
X
15
pkt p. 11
12 in.
15 in.
Which figures are similar?
20 in.
For each rectangle, find the ratio
of the length of the short side
to the length of the long side.
10 in.
6 in.
6 in.
A
B
C
D
9 in.
20 in.
12 : 20
6 : 10
9 : 15
6 : 20
12
3
= 5
20
6
3
10 = 5
9
3
=
15
5
3
6
= 10
20
B, C
A, C
A, B
not similar
Similar rectangles have the SAME ratio!
Non-similar rectangles have different ratios!
A
12 : 20
B
6 : 10
C
9 : 15
D
6 : 20
12
3
= 5
20
6
3
10 = 5
9
3
=
15
5
3
6
= 10
20
B, C
A, C
A, B
not similar
4. Choose two similar rectangles.
Find the scale factor from the smaller to the larger.
B to A = 2
B to C = 1.5 C to A = 4/3
What does the scale factor tell you?
How many times greater or smaller each
side length and perimeter will be.
A
12 : 20
B
6 : 10
C
9 : 15
D
6 : 20
B to A = 2
12
3
= 5
20
6
3
10 = 5
9
3
=
15
5
3
6
= 10
20
B, C
A, C
A, B
not similar
B to C = 1.5 C to A = 4/3
5. Compare the information given by
the scale factor to the information given by
the ratios of side lengths.
Did I Hit My Learning Target?
I can use equivalent ratios to compare
corresponding sides of similar rectangles.
Homework:
Complete notes for Inv 4.2 on p. 12 –
for the Zaption video 4.2
EXTRA PRACTICE:
• F and G are similar. They have the same angle measure for
corresponding angles. AND, each of the corresponding sides
has the same scale factor.
• For each parallelogram, find the ratio of the length of a long
side to the length of a short side. How do the ratios compare?
Ratio for E
10
8
= Ratio for F
They all have equal ratios:
7.5
6
= 𝑅𝑎𝑡𝑖𝑜 𝑓𝑜𝑟 𝐺
6
4.8
Scale Factor:
B to A = 2
Ratio of short side to long side
B to C = 1.5
C to A =
Similar figures have a constant scale factor and their ratios of
corresponding side lengths will be equivalent.
The scale factor gives the amount of stretching (or shrinking)
from the original figure to the image.
The ratio of adjacent side lengths within a figure gives an
indication of the shape of the original figure (and image),
since it compares measures within one figure.