7.1 Ratio and Proportion
Textbook page 357
ratio
A comparison of a number a and a
nonzero number b using division.
 The ratio of a to b can be written as:

a
a fraction b
 as a:b
 or as “a to b”

(or an equivalent decimal)
simplify the ratio 60 cm to 200 cm
60 cm
Rewrite as a fraction 200 cm
 Divide the numerator and the denominator
by the greatest common factor

60 cm / 20
200 cm / 20

Simplify as
3 cm
10 cm
simplify the ratio 3 ft to 18 in
3 ft
Rewrite as a fraction 18 in
 Make sure the units are the same, then
divide the numerator and the denominator
by the greatest common factor

3 ft * 12 in
18 in

=
36 in
36 in / 18
18 in
18in / 18
Simplify as
2 in
1 in
The perimeter of a rectangle is 84 ft. The ratio of the
length to the width is 4:3. Find the length and width of
the rectangle.
length : width
P = 2l + 2w
4:3
P = 2(4x) + 2(3x)
84 = 8x + 6x
84 = 14x
___
___
14
14
length
6
6
6
6
6
X=6
6
length = 4(6) = 24 units
6
width = 3(6)
= 18 units
width
Proportions







An equation that states that two fractions are
equal
extreme
mean
a= b
mean
extreme
c d
b and c are the means
a and d are the extremes
Multiply the means and extremes – the cross
products are equal.
bc = ad
Solve the resulting equation
5=y+2
3
6.






3( y + 2)
3y + 6
-6
3y
3
=
=
=
y = 8
5(6)
30
-6
24
3
Examples on pg 358 - 359
1)
 3)
 4)
 5)

EF = 16, FG = 8
x=4
y=9
m=5
Homework
Assignment # 3
 Pg 361
 Problems 1-46, 56-61
