Slide 1

Blue day – 3/9/15
Gold day – 3/10/15


Slide 2

Word problems with linear equations will be
in slope-intercept form if you are given the
following information:
•the slope (m) - the rate of change

•the y-intercept (b) - the starting (initial) value


Slide 3

A closet organizer charges a $100 initial consultation fee plus
$30 per hour. The cost as a function of the number of hours
worked is graphed below.

a. Write an equation that
represents the cost as a
function of the number of
hours.
Cost

is

$30

y

=

30

for each
hour
•x

An equation is y = 30x + 100.

plus

$100

+

100


Slide 4

A closet organizer charges $100 initial consultation fee plus $30
per hour. The cost as a function of the number of hours worked
is graphed below.
b. Identify the slope and y-intercept and describe their
meanings.
The y-intercept is 100. This is the cost for 0 hours, or the initial fee
of $100. The slope is 30. This is the rate of change of the cost: $30
per hour.

c. Find the cost if the organizer works 12 hrs.
y = 30x + 100
= 30(12) + 100 = 460

Substitute 12 for x in the equation

The cost of the organizer for 12 hours is $460.


Slide 5

A caterer charges a $200 fee plus $18 per person served. The cost
as a function of the number of guests is shown in the graph.

a. Write an equation that represents the
cost as a function of the number of
guests.
Cost

is

$18

y

=

18

for each
meal
•x

plus

$200

+

200

An equation is y = 18x + 200.


Slide 6

A caterer charges a $200 fee plus $18 per person served. The cost
as a function of the number of guests is shown in the graph.

b. Identify the slope and y-intercept and describe their
meanings.
The y-intercept is 200. This is the cost for 0 people, or the

initial fee of $200. The slope is 18. This is the rate of change
of the cost: $18 per person.

c. Find the cost of catering an event for 200 guests.
y = 18x + 200
= 18(200) + 200 = 3800

Substitute 200 for x in the equation

The cost of catering for 200 people is $3800.


Slide 7



Suppose that the water level of a river is
34 feet and that it is receding at a rate of
0.5 foot per day. Write an equation for
the water level, L, after d days. In how
many days will the water level be 26 feet?


Slide 8



For babysitting, Nicole charges a flat fee
of $3, plus $5 per hour. Write an
equation for the cost, C, after h hours of
babysitting. What do you think the slope
and the y-intercept represent? How much
money will she make if she baby-sits 5
hours?


Slide 9



A plumber charges $25 for a service call
plus $50 per hour of service. Write an
equation in slope-intercept form for the
cost, C, after h hours of service. What will
be the total cost for 8 hours of work? 10
hours of work?