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Solve the following proportions
a 27

6 18
c  2 3c

4
18
b  3 15

8
12
d 4
4

5
d 4
Solve the following proportions
a 27

6 18
a=9
c  2 3c

4
18
c=6
b  3 15

8
12
b=7
d 4
4

5
d 4
d = ±6
Using Proportions to
Solve Geometry
Problems
Sections 6.1-6.3
Ratios & Proportions
• A ratio is a comparison of two values, usually showed as a
fraction.
a
b
• A proportion is an equation in which two ratios are set equal
to each other.
a c

b d
Properties of Proportions
The proportion is still equal if:
1. You take the reciprocal of both sides.
2. You switch the numbers along one or
both diagonals.
3. You add the value in the denominator
to the numerator on both sides.
Using proportions
• The measures of the angles of a triangle are in the ratio of
3:5:10. What are the measures of each angle?
• The measures of the angles of a different triangle are in the
ratio of 11:12:13. What are the measures of each angle?
Assignment
• Pg. 360 #3-9 odds, 19-29 odds, 42-45 all
• Pg. 367 #3-12 all