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Question 964122: a basic cellular phone plan costs $18 per month for 50 calling minutes. Additional time costs $0.30 per minute. The formula C = 18+0.30 (x-50) gives the monthly cost for this plan for calling minutes, where x > 50. How many calling minutes are possible for a monthly cost of minimum $30 and a maximum $45?
a. minimum 40 minutes and maximum 90 minutes
b. minimum 12 minutes and maximum 27 minutes
c. minimum 90 minutes and maximum 140 minutes
d. minimum 30 minutes and maximum 45 minutes
Answer by macston(5194)   (Show Source):
You can put this solution on YOUR website! .
C = 18+0.30 (x-50) Subtract 18 from each side.
C-18=0.30(x-50) Divide each side by 0.30
(C-18)/0.30=x-50
(C/0.30)-(18/0.30)=x-50
(C/0.30)-60=x-50 Add 50 to each side.
(C/0.30)-10=x
.
For C=$30:
($30/0.30)-10=x
100-10=x
90=x ANSWER 1:For $30/month, there are 90 minutes available
.
For C=$45:
($45/0.30)-10=x
150-10=x
140=x ANSWER 2: For $45, there are 140 minutes available
ANSWER: The correct choice is C.
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