8
8
x
1
8
.6
x
0.2
Therefore, Priscilla takes 0.2 hours to ride from home to school.
Now let’s do the same calculations for her trip from school to home:
Unknown
time
to ride from school to home
y
Known
rate from home to school
4 mph
Known
distance
from school to home
total distance round-trip
2
3.2
miles
2
1.6 miles
Then, use the formula (Rate)(Time)
Distance to write an equation:
(Rate)(Time)
Distance
4
x
1.6
4
4
x
1
4
.6
x
0.4
Therefore, Priscilla takes 0.4 hours to ride from school to home.
Finally add the times for each leg to determine the total time it takes Priscilla to complete the round
trip:
0.4
0.2
0.6 hours
It takes Priscilla 0.6 hours to complete the round-trip.
Wo r k - O u t p u t P r o b l e m s
Work-output problems deal with the rate of work. In
other words, they deal with how much work can be com-
pleted in a certain amount of time. The following formula can be used for these problems:
(rate of work)(time worked)
part
of job completed
Example
Ben can build two sand castles in 50 minutes. Wylie can build two sand castles in 40 minutes. If Ben and Wylie
work together, how many minutes will it take them to build one sand castle?
Since Ben can build two sand castles in 60 minutes, his
rate of work is
2
6
s
0
an
m
d
in
ca
u
s
t
t
e
l
s
es
or
1
3
s
0
a
m
nd
in
c
u
a
t
s
e
tl
s
e
. Wylie’s rate of
work is
2
4
s
0
an
m
d
in
ca
u
s
t
t
e
l
s
es
or
1
2
s
0
a
m
nd
in
c
u
a
t
s
e
tl
s
e
.
To solve this problem, making a chart will help:
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