CK-12 Geometry Concepts

http://www.ck12.org Chapter 7. Similarity

a= 3960. 81 ,b= 5941. 21 ,c= 8911. 82

Vocabulary

Pairs of numbers areproportionalif they are in the same ratio. Two lines areparallelif they have the same slope
and thus never intersect. Atransversalis a line intersecting a system of lines.

Guided Practice

Finda,b,andc.

Look at the corresponding segments. Only the segment marked “2” is opposite a number, all the other segments are
opposite variables. That means we will be using this ratio, 2:3 in all of our proportions.

a

2

=

9

3

2

4

=

3

b

2

3

=

3

c

3 a= 18 2 b= 12 2 c= 9

a= 6 b= 6 c= 4. 5

There are several ratios you can use to solve this example. To solve forb, you could have used the proportion^64 =^9 b,
which will still give you the same answer.

Practice

Find the value of each variable in the pictures below.

1.

2.

3.

4.

5.

The street map shows part of New Orleans. Burgundy St., Dauphine St. and Royal St. are parallel to each other. If
Spain St. is perpendicular to all three, find the indicated distances.

6. What is the distance between pointsAandB?


7. What is the distance between pointsCandD?


8. What is the distance between pointsAandD?

Using the diagram, answer the questions.

9. What is the value ofw?


10. What is the value ofx?


11. What is the value ofy?


12. What is the length ofAB?


13. What is the length ofAC?