Basic Mathematics for College Students

679

Check
If the band’s fee was $600, and we divide it into 5 equal parts, we should get the
amount that each player earned.

This is the amount each band member earned.

The result, $600, checks.



120

(^5)  600
 5
10
 10
00
 0
0
EXAMPLE (^5) Volunteer Service Hours To receive a degree in child
development,students at one college must complete 135 hours of volunteer service
by working 3-hour shifts at a local preschool. If a student has already volunteered
87 hours, how many more 3-hour shifts must she work to meet the service
requirement for her degree?
Analyze

• Students must complete 135 hours of volunteer service. Given


• Students work 3-hour shifts. Given


• A student has already completed 87 hours of service. Given


• How many more 3-hour shifts must she work? Find

Form
Let x  the number of shifts needed to complete the service requirement. Since
each shift is 3 hours long,multiplying 3 by the number of shifts will give the number
of additional hours the student needs to volunteer.

87  3  x  135

Solve
We need to isolate x on the left side.

Do the subtraction.

Do the division.

State
The student needs to complete 16 more 3-hour shifts of volunteer service.

Check
The student has already completed 87 hours.If she works 16 more shifts,each 3 hours
long, she will have 16  3  48 more hours.Adding the two sets of hours, we get:

This is the total number of hours needed.

The result, 16, checks.



87

 48

135

x  16

To isolate x, divide both sides by 3 to undo

(^) the multiplication by 3.
3 x
3



48

3

3 x  48

To isolate the variable term 3x, subtract 87

87  3 x  87  135  (^87) from both sides to undo the addition of 87.
87  3 x  135
the number
of hours
required.
is
the number of
shifts yet to be
completed
plus 3 times
The number of
hours she has
already completed
Self Check 5
SERVICE CLUBS To become a
member of a service club,
students at one college must
complete 72 hours of volunteer
service by working 4-hour shifts
at the tutoring center. If a
student has already volunteered
48 hours, how many more 4-
hour shifts must she work to
meet the service requirement
for membership in the club?
Now TryProblem 23
1 3
12
5
15
 8 7
4 8
16
3  48
 3
18
 18
0