6th Grade Math Textbook, Progress

Solve Proportions

11-5

You can use the cross-products rule

to solve a proportion.

Solve the proportion: 


2

n

5





6

5


.

Extremes Means

3 :8 n: 24 3  24  8 n

572  8 n

5 72  8  8 n 8

9 nor n 9

Check: 
^3

8

 


2

9

4

 
^3

8


^3

8

?



Complete to find the missing term in each proportion.

1. 
   n
   6


^5

3

 n 3  6  5 2. 
^8

n


^3

4

2

0

 8  40 n 32

 3 n  30  320   32 n

 3 n?? n

????

Study these examples.

Extremes Means


^3

n

(^0)

6
5

30  5 n 6
 150  6 n
150  6  6 n 6
 525 nor n 25
Check:
^3
2
0
5


^6
5


^6
5


^6
5


?

Method 1
Find the cross products. The product
of the extremes is equal to the
product of the means.
Extremes Means


2
n
5



6
5

n 5  25  6
5 n 5  150  5
 5 n 30
Check by substituting the solution for n.
Check:

3
2
0
5



6
5

30  5 25  6 150  150
?

?

Method 2
Multiply each side of the proportion by
the reciprocal.


2
n
5



6
5

 

6
5


n 30
25
1
25
1
n
25
1 1
1 5
1.3
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