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.
- 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
8206-2_384-385 10/7/07 12:04 PM Page 384