Pre-Algebra Demystified

In problems involving proportions, there will always be a ratio statement.
It is important to find the ratio statement and then set up the proportion
using the ratio statement. Be sure to keep the identical units in the numer-
ators and denominators of the fractions in the proportion.

EXAMPLE

An automobile travels 176 miles on 8 gallons of gasoline. How far can it go
on a tankful of gasoline if the tank holds 14 gallons?

SOLUTION

The ratio statement is:

176 miles

8 gallons

so the proportion is:

176 miles

8 gallons

¼

x miles

14 gallons

Solve:

176

8

¼

x

14

8x¼ 14  176

8x¼ 2464

8 x

8

¼

2464

8

x¼308 miles

Hence, on 14 gallons, the automobile can travel a distance of 308 miles.

Math Note: Notice in the previous example that the numerators of

the proportions have the same units, miles, and the denominators have

the same units, gallons.

EXAMPLE

If it takes 16 yards of material to make 3 costumes of a certain size, how
much material will be needed to make 8 costumes of that same size?

CHAPTER 8 Ratio and Proportion 157