Chapter 8 linear appliCaTionS 273
The equation to solve is^1
45
1
30
+ = ^1.
t
The LCD is 90t.
1
45
1
30
1
90 1
45
1
30
90 1
90 1
45
+=
+
=
t
tt
t
t
+
=
+=
=
=
=
90 1
30
90
2390
590
90
5
18
t
tt
t
t
t
Joe and Jerry can mow the lawn in 18 minutes.
Tammy can wash a car in 40 minutes. When working with Jim, they can
wash the same car in 15 minutes. How long would Jim need to wash the car
by himself?
Let t represent the number of minutes Jim needs to wash the car by himself.
Worker Quantity Rate Time
Tammy 1 1/40 40
Jim 1 1/t t
Together 1 1/15 15
The equation to solve is^1
40
11
15
+ = .
t
The LCD is 120t.
1
40
11
15
120 1
40
1 120 1
15
120 1
40
+=
+
=
t
t
t
t
t
+
=
+=
−−
=
120 1 8
3 120 8
33
120 5
120
t
t
t
tt
tt
t
55
24
=
=
t
t