Answers to Homework

2) 1:1 4) 5:1 6) 6 to 5

8) 11 to 12 10) 11/17 12) 6:5:12

14) 6:11:17 16) 5:3 18) 20:17

20) 1:5 22) 2d/5c 24) 40,50

26) 45,60,75 28) 67.5,67.5,45

30) 32,44,56

7-2 Properties of Proportions

Proportion = 2 equal ratios

same as

cross multiply

swap

reciprocal

add bottom #

then

ad bca c

b d

a c a c

b d b d

b d

a c

a b

c d

a b c d

b d

Example

First

Outer

Inner

Last

2 22 1 2 4 2 8x x x x x x

1 4

2 2

x x

x x

( 1)( 2) ( 2)( 4)x x x x

2 22 2 8x x x x 2 2 8x x 2 8x

6x

Try On Own (both answers are fractions)

1)

2)

Answers:

1) x = 10/3

2) x = -20/3

2

5

x x

x x

5

2 4

x x

x x

Example

A

B

CDE

AB ED

BC DC

What else do you know?AB BC AC ED DC EC

Given ED = 2, DC = 6, and AB = 3Find BC, AC, and EC.

3

62

EC = 2 + 6 = 8

3 2

6BC 2BC = 18, BC = 9

AC = 3 + 9 = 12

Example

A

B

CDE

AB ED

BC DC

Given AB = 12, BC = 4, and EC = 20Find ED, DC, and AC.

12

4

20

AC = 12 + 4 = 16

12

4 20

x

x

Cross Multiply, ED = 15

DC = 20 – 15 = 5x 20 – x

TOO

A

B

CDE

AB ED

BC DC

1)Given AB = 8, AC = 10, and ED = 12 Find BC, DC, and EC.

2)Given AC = 30, ED = 28, and EC = 42 Find AB, BC, and DC.

1) BC = 2 DC = 3 EC = 15

2) AB = 20 BC = 10 DC = 14

Homework

Pg 247 #1-8 all

9-27 odd

33-35 all