unit 7: similarity (7.1) ratios and proportions lt: write and solve proportions
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Unit 7: Similarity(7.1) Ratios and Proportions
LT: Write and solve proportions
Ratios
Ratio: A comparison of two quantities by division.
1) The ratio of a to b
2) a : b
3) a
b, b0
Ratios can be written in three ways…
5 in.
Ratios
6 in.
1 ¾ ft.
2 ft.
Find the ratio of the width of the photo to the poster.
Proportions
Proportion: A statement that two ratios are equal.
a
bc
dor a :bc : d
Determine if each of the following pairs of ratios are equal.
1) 1: 2 5 :105
3
3
5 2)
3) 10
15
18
27= ≠ =
Proportions
Properties of Proportions: is equivalent to…
a
bc
d
1) ad bc
2) b
ad
c
3) a
cb
d
4) a bb
c dd
Cross-Product Property: The product of the extremes is equal to the product of the means.
If , complete each statement.
Applying Properties
x
y
5
6
1) 6x
2) y
x
3) x
5
4) x yy
Solving Proportions
Solve the following proportions.
1) x
6
12
8
2) y 3
8y
4
3) 5
z
20
3
Ratios
Scale: The ratio of any length in a scale drawing to the corresponding actual length.
Ex. 1cm to 1ft or 1in = 10ft or 1mm : 100mi
An inch ruler shows that l = 7/8 in.Find the actual length of the bedroom.
7.1 Ratios and Proportions
HW (7.1): Pgs. 368-370; 1-29 odd, 43, 44
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