284 algebra De mystif ieD

(^) Worker Quantity Rate Time
Jeremy 1 1/60 60
Sarah 1 1/90 90
Together 2/3 2
3
23 2
3
t
tt

t
The equation to solve is^1
60
1
90
2
3
+=
t

. The LCD is 180t.

1

60

1

90

2

3

180 1

60

1

90

180 2

3

180 1

60

+=

+











=⋅





t

tt

t

t 



+ 







=

+=

=

=

=

180 1

90

120

32120

5 120

120

5

24

t

tt

t

t

t

They will need 24 minutes to finish the lawn.

4. (a) Let t represent the number of hours the presses need, working
   together, to complete the job.

(^) Worker Quantity Rate Time
Press 1 1200 t 1200 t
Press 2 1500 t 1500 t
Together 45,000 45,000/t t
The equation to solve is 1200t + 1500t = 45,000. (Another equation
that works is 1200 + 1500 = 45,000/t.)
1200 1500 45 000
2700 45 000
45 000
2700
162
tt
t
t
t
+=

=

,
,
,
33