Algebra Demystified 2nd Ed

236 algebra De mystif ieD

We begin by substituting numbers given in the question for variables in

the formula.

(a) The height is 6 inches, so h = 6. Then V = 100h becomes V = 100(6) = 600.

The box’s volume is 600 cubic inches.

(b) The volume is 450 cubic inches, so V = 450, and V = 100h becomes

450 = 100h.

450 100

450

100

45

=

=

=

h

h

. h
The box’s height would need to be 4.5 inches.
(c) The volume is 825, so V = 100h becomes 825 = 100h.
825 100
825
100
825

=

=

=

h

h

. h
The height should be 8.25 inches.

A square has a perimeter of 18 cm. What is the length of each of its

sides?

We recall the formula for the perimeter of a square: P = 4l where l is the

length of each of its sides.

P = 18; so P = 4l becomes 18 = 4l.

18 4

18

4

45

=

=

=

l

l

. l
The length of each of its sides is 4.5 cm.
The relationship between degrees Fahrenheit and degrees Celsius is given
by the formula CF=−^59 () 32. At what temperature will degrees Fahrenheit
and degrees Celsius be the same?