Transcript Buying on Credit

On a group quiz, your group needs to calculate the answer to
12 – 2 * 6 – 3.
The three other group members came up with these answers:
Marta: 57
Matt: -3
Miguel: 30
1. Who, if anyone, is correct?
Matt
2. What would you say to the other group members to
convince them?
Follow the order of operations.

Students will:
◦ Use the equation of a linear model to make
predictions about the data
Electric Avenue sells audio/video, computer,
and entertainment products. The store offers
0% interest for 12 months on purchases made
using an Electric Avenue store credit card.
1. Emily purchases a television for $580 using
an electric Avenue store credit card. Suppose
she pays the minimum monthly payment of $25
each month for the first 12 months.
a. Complete a table of (number of monthly
payments, account balance) values for the first 6
months after the purchase, then plot those
values on a graph.
Number of Monthly Payments
Account Balance (in dollars)
0
1
$580 $555
2
3
$530 $505
4
5
6
$480 $455 $430
b. Will Emily pay off the balance within 12 months?
No; Her balance isn’t 0 after
How do you know?
12 payments of $25. It’s $280.
c. If you know Emily’s account balance NOW, how
can you calculate the NEXT account balance, after a
monthly payment? Next = Now – 25; Start at 580.
d. Which of the following function rule(s) gives
Emily’s account balance E after m monthly payments
have been made? E = -25m + 580 or E = 580 – 25m
E = 25m – 580 E = m – 25
E = -25m + 580
E = 580 + 25m
E = 580 - 25m
e. Determine the rate of change, including units, in
the account balance as the number of monthly
payments increases from:
0 to 2;
-$50/2 = -$25/month
-$25/1 = -$25/month
2 to 3;
3 to 6;
-$75/3 = -$25/month
i. How does the rate of change reflect the fact
that the account balancedecreases as the number of
monthly payments increases? Negative Slope
ii. How can the rate of change be seen in the
graph from Part a? In the function rule(s) you
selected in Part d? Balance decreases as number
of payments increases
-25
f. How can the starting account balance be seen
in the table in Part a? Payment #0 or (0, 580)
In the graph?
y-intercept
In the function rule(s) you selected in Part d?
Start at value or y-int
2. The diagram shows graphs
of account balance functions
for three Electric Avenue
customers.
Ellen: E = 480 – 20m
E
F
D
Darryl: D = 480 – 40m
Felicia: F = 360 – 20m
a. Match each function rule with its graph. Explain how you
could make the matches without calculations or graphing
tool help (calculator). Slope and y-intercept differences.
b. What do the numbers in the rules for Ellen’s and Felicia’s
account balances tell you about the values of their
purchases and their monthly payments? Different start amount, same
spending rate.
c. What do the numbers in the rules for Darryl’s and Felicia’s
account balances tell you about the values of their
Different start amount,
purchases and their monthly payments? different spending rate.
CW1: Buying on Credit
CW2: Buying / Selling on Credit WS
HW: Hooke’s Law