Algebra Demystified 2nd Ed

Chapter 8 linear appliCaTionS 233

6. 18 18
   18
   18
   18 10
   1810
   180
   18

10 1000

()

.()

%

x

x

x

x

=

=

=

===

18 is 1000% of 1.8.

7. 2 1
   4
   1
   2

1

4

1

8

0 125 125

x

x

x

=

=⋅

==..= %

41 is 12.5% of 2.

8.

1

4

2

42

8 800

x

x

x

=

=

==

()

%

2 is 800% of^14.

Working with Formulas

For some word problems, nothing more is required other than to plug a given
value into a formula, which is either given or is readily available. The most dif-
ficult part of these problems is to decide which variable the given quantity
should represent. For example, the formula might look like R = 8q and the
value given to you is 440. Is R = 440 or is q = 440? The answer lies in the way
the variables are described. In R = 8q, suppose R represents revenue (in dollars)
and q represents quantity (in units) sold of some item. In the question, “If
440 units were sold, what is the revenue?” q is 440. We would then solve
R = 8(440). In the question, “If the revenue is $440, how many units were
sold?” 440 is R, and we would solve 440 = 8q.