Questions (contd)
(a) For what amount of driving do the two plans cost the same?
(b) What is the cost when the two plans cost the same?
Answer:
(a) 100 miles
(b) $65
Step-by-step explanation:
Given
Plan 1:
[tex]Initial\ Fee = \$57[/tex]
[tex]Additional = \$0.08[/tex] per mile
Plan 2:
[tex]Initial\ Fee = \$50[/tex]
[tex]Additional = \$0.10[/tex] per mile
Solving (a): Number of miles when both plans are equal
Represent the distance with x and the cost with y
So:
Plan 1:
[tex]y = 57 + 0.08 * x[/tex]
Plan 2:
[tex]y = 50 + 0.10 * x[/tex]
To solve (a), we equate both plans together; i.e.
[tex]y = y[/tex]
[tex]57 + 0.08x = 50 + 0.10x[/tex]
Collect Like Terms
[tex]0.08x - 0.10x= 50 - 57[/tex]
[tex]-0.02x= -2[/tex]
Solve for x
[tex]x = -2/-0.02[/tex]
[tex]x = 100[/tex]
Hence, 100 mile would cost both plans the same
Solving (b): Cost when both plans are the same:
In this case, we simply substitute 100 for x in any of the y equation.
[tex]y = 57 + 0.08 * x[/tex]
[tex]y = 57 + 0.08 * 100[/tex]
[tex]y = 57 + 8[/tex]
[tex]y = 65[/tex]
Hence, the amount is $65
