Post on 11-Jan-2016
3.1 Systems of Linear Equations
Word Problems
Word Problemsp.122 #37
37) To pay your monthly bills, you can either open a checking account or use an online banking service. A local bank charges $3 per month and $0.40 per check, while an online service charges a flat fee of $9 per month.
a) Write and graph a system of linear equations to model the cost c of each service for b bills that you need to pay monthly.
b) Find the point of intersection of the two linear models. What does this answer represent?
c) If you pay about 12 bills per month, which service should you choose? Explain
p. 122 #37
a) Write and graph a system of linear equations to model the cost c of each service for b bills that you need to pay monthly.
p. 122 #37
a) Write and graph a system of linear equations to model the cost c of each service for b bills that you need to pay monthly.
Checking account:
$3/month, $0.40 per bill
Online banking:
Fixed cost of $9
p. 122 #37
a) Write and graph a system of linear equations to model the cost c of each service for b bills that you need to pay monthly.
Checking account: c = $3 + $0.40b
Online banking: c = $9
p. 122 #37Checking account: c = $3 + $0.40b
Online banking: c = $911
10
9
8
7
6
5
4
3
2
1
0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Monthly cost
($)
Number of monthly bills
p. 122 #37Checking account: c = $3 + $0.40b
Online banking: c = $911
10
9
8
7
6
5
4
3
2
1
0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Monthly cost
($)
Number of monthly bills
p. 122 #37Checking account: c = $3 + $0.40b
Online banking: c = $911
10
9
8
7
6
5
4
3
2
1
0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Monthly cost
($)
Number of monthly bills
p. 122 #37Checking account: c = $3 + $0.40b
Online banking: c = $911
10
9
8
7
6
5
4
3
2
1
0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Monthly cost
($)
Number of monthly bills
p. 122 #37b) Find the point of intersection of the two linear models.
What does this answer represent?
11
10
9
8
7
6
5
4
3
2
1
0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Monthly cost
($)
Number of monthly bills
p. 122 #37b) Find the point of intersection of the two linear models.
What does this answer represent?
11
10
9
8
7
6
5
4
3
2
1
0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Monthly cost
($)
Number of monthly bills
p. 122 #37b) Find the point of intersection of the two linear models.
What does this answer represent?
11
10
9
8
7
6
5
4
3
2
1
0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Monthly cost
($)
Number of monthly bills
Intersection = (15, 9)
p. 122 #37b) Find the point of intersection of the two linear models.
What does this answer represent?
The point of intersection is where the two linear models are equal.
It represents where the cost of using the bank or online service would be the same.
p. 122 #37
c) If you pay about 12 bills per month, which service should you choose? Explain
p. 122 #37
c) If you pay about 12 bills per month, which service should you choose? Explain
The local bank would be cheaper if you only have 12 bills to pay per month.
Homework
p.122 #44, 45, 55