7.1 Ratios and Proportions
Ratios
Ratio: A comparison of two quantities by division.
Ratios can be written in three ways…
1) The ratio of a to b
2) a : b
3)

a
, b0
b
Ratios
Find the ratio of the width of the photo to the poster.
5 in.
6 in.
1 2/3 ft.
2 ft.
Proportions
Proportion: A statement that two ratios are equal.
a c

b d
or a : b  c : d
Determine if each of the following pairs of ratios are equal.

1) 1: 2 = 5 :10
5 3
2) ≠
3 5
3)

10 18
=
15 27
Proportions
a c
Properties of Proportions:  is equivalent to…
b d
b d
a b
ab c  d
1) ad  bc
2) 
3) 
4)

a c
c d
b
d

Cross-Product Property: The product of the extremes is equal to
 of the means.


the product
Applying Properties
x 5
If  , complete each statement.
y 6
1) 6x 
y
2) 
x
3)
x

5
4)
xy

y
Solving Proportions
Solve the following proportions.
y3 y
2)

8
4
x 12
1) 
6 8

5 20
3) 
z 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.
Ratios
Scale Drawing Activity!!!
20 point QUIZ grade
#1-5 worth 2 points each
#6 worth 10 POINTS!
No more than 4 in a group
•Must set up a proportion for each problem
•Show all work on every problem
•Answers must have the correct units of measure
7.1 Ratios and Proportions
Homework #1
Pg 368 #2, 3-21 odd, 27, 30, 31,
35-43 odd