8.2 Problems with Proportions
Use Properties of Proportions
True or Not
These proportions are true
a c
d c
a b
    
b d
b a
c d
State if the following Proportions are correct.
x 15
x 15

 
10 y
y 10
x c
x y cz
 

y z
y
z
True or Not
These proportions are true
a c
d c
a b
    
b d
b a
c d
State if the following Proportions are correct.
x 15
x 15

 
10 y
y 10
x c
x y cz
 

y z
y
z
x
c
1  1
y
z
MQ LQ

NQ PQ
Find LQ
Solve for x first
M
6
N
13
L
15
5
P
x
Q
MQ LQ

NQ PQ
Find LQ
Solve for x first
M
15
x

6  15 x  5
6
N
13
15
15 x  15  21x
L
5
P
x
Q
MQ LQ

NQ PQ
Find LQ
Solve for x first
M
15
x

6  15 x  5
6
N
13
15
15 x  15  21x
15 x  75  21x
75  6 x
x  12.5
L
5
P
x
Q
MQ LQ

NQ PQ
Find LQ
Solve for x first
M
15
x

6  15 x  5
6
LQ  5  12.5
N
13
15 x  15  21x
15 x  75  21x
75  6 x
x  12.5
L
LQ  17.5
15
5
P
x
Q
Geometer mean of a number
Definition of geometer mean :
The central number in a geometric
progression (e.g., 9 in 3, 9, 27), also
calculable as the nth root of a product
of n numbers.
How to find the geometer mean of 10 and 15.
Let x be the
x 15
2
geometer
  x  10(15)
10 x
mean
Geometer mean of a number
x 15
2
  x  10(15)
10 x
x  10(15)
x  2553
x  5 23
x5 6
Find the Geometric mean
of 35 and 175
Set up the fraction or the square root.
35
x

 x 2  35175
x 175
x  35175
x  57 57 5
x  35 5
Find the Geometric mean
of 35 and 175
Set up the fraction or the square root.
35
x

 x 2  35175
x 175
x  35175
x  35175
x  35  35  5
x  57 57 5
x  35 5
x  35 5
Homework
Page 468 – 471
# 10 – 28 even
32 – 35, 38,
44, 47 - 50