Math 110 Technical Writing Assignment #2: Creating and Interpreting Functions
Focus:



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Creating and Interpreting Functions
Always define variables.
Explain how the function is created. Use verbal explanations and calculations as appropriate.
Explain what the parameters of the function mean in the context of the problem.
Explain answers to requested calculations.
Reminder: Read back through your previous technical writing information before completing this
assignment.
Example: In a college meal plan you pay a membership fee; then all your meals are at a fixed price per
meal.
a) If 30 meals cost $152.50 and 60 meals cost $250, write a function to model this situation.
b) Find the cost for 50 meals.
c) Determine the maximum number of meals you can buy on a budget of $300.
Important points:
 Situation is summarized
in introduction
 Variables are defined
 The response is written
as one complete piece
and is not broken into
parts a, b, c from the
question.
 The steps in creating the
function are explained
and shown
 The function is given
 Parts of the function are
interpreted in context
 Calculations are
introduced verbally and
then shown symbolically
 Results of calculations
are interpreted in context
in complete sentences.
 Result of last calculation
is rounded appropriately
for the context.
A college meal plan is based on a membership fee plus a price per meal. Thirty
meals cost $152.50 and 60 meals cost $250. To find a model for this situation, let n
be the number of meals and P be the total price in dollars. The number of meals is
the independent variable and the price of those meals is the dependent variable. In
order to write a linear function for this situation, both the slope and vertical
intercept will be found. In addition, the cost for 50 meals and the number of meals
that can be bought for $300 will be determined.
First the slope is found using the ordered pairs (30, 152.50) and (60, 250):
slope  m 
P2  P1 250  152.50 97.5


 3.25
n2  n1
60  30
30
Using the slope, the vertical intercept can be found by using one of the ordered
pairs.
P(n)  3.25n  b
250  3.25(60)  b
250  195  b
55  b
The model for the meal plan is P (n)  3.25n  55 . The vertical intercept
represents the membership fee of $55. The slope represents a cost of $3.25 per
meal.
This function can be used to find the cost of 50 meals by evaluating the function for
n = 50:
P(50) = 3.25(50)+55
P(50)=217.5
So 50 meals cost $217.50. To find how many meals a person can get for $300,
substitute $300 in for P and solve for n.
300 = 3.25n +55
245 = 3.25n
75.384 = n
$300 will buy 75 meals.
Math 110 Technical Writing Assignment #2: Equations and Calculations
Date Assigned:
Date Due:
Monday, February 4
Friday, February 8
Assignment:
In 2007, there were 86,927 inmates in juvenile facilities in Colorado. In 2012 there were approximately
80,000 juvenile inmates in Colorado.
a. Write the linear function to model this situation.
b. Identify the domain and range for this function. Justify your reasoning and include any
calculations that were necessary in determining these answers.
Rubric:
Item
A
Properly formatted (typed, double spaced, stapled, rubric attached)
B
Complete sentences with proper grammar, spelling, punctuation
C
Language is precise (limited use of pronouns, correct terminology, etc.)
D
Introduction summarizes important information
E
Completely and correctly answers the question(s)
F
All variables are identified (letter, what it represents, units, ind/dep)
G
Equation/formula/model is given AND parts of equation are identified/interpreted
H
Calculations are introduced verbally AND mathematical steps are shown
I
Results of calculations are interpreted in a complete sentence
Total Points
Points