EXAMPLE

Multiply the expression 3 : 2 by 2.

3:2=6:4

Multiplying

both

terms

by

2

renders

the

expression 6 : 4. Check by dividing 3 by 2 which

renders a ratio of 1.5. In the second expression

dividing 6 by 4 also renders a ratio of 1.5.

Thus, 3 : 2 is equal in value to 6 : 4.

Divide the expression 8 :

4 by 4.

8:4=2:1

Dividing both terms by 4 renders the expression

2 : 1.

Check by dividing 8 by 4 in the first

expression, which renders a ratio of 2. In the

second expression dividing 2 by 1 renders a ratio

of 2. Thus 8 : 4 is equal in value to 2 : 1.

c.

(1) Proportion is a statement of equality between two ratios. Thus, 3 : 4

: : 6 : 8. The symbol (: :) means "as" or "equals." Either this symbol or

the equal sign (=) may be used.

The "extremes' are the first and last

terms. The "means" are the second and third terms.

(2) *Rule 1*. In proportion, the product of the means equals the product of

the extremes.

EXAMPLE

Therefore, 3 : 4 : : 9 : 12.

4 x 9 = 36

Multiply the means.

3 x 12 = 36

Multiply the extremes.

Thus, the two expressions

are equal.

when three terms of a proportion are known the fourth can be found.