SOLUTION: At the car wash there is a flat fee for the first 8 minutes. Sally was there for 12 mins and cost her $5. John was there for 17 mins and cost him $6.25. Write a equation and find t
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Question 456897: At the car wash there is a flat fee for the first 8 minutes. Sally was there for 12 mins and cost her $5. John was there for 17 mins and cost him $6.25. Write a equation and find the cost of the flat fee and cost per minute. Answer by ankor@dixie-net.com(22740) (Show Source):
You can put this solution on YOUR website! At the car wash there is a flat fee for the first 8 minutes.
Sally was there for 12 mins and cost her $5.
John was there for 17 mins and cost him $6.25.
Write a equation and find the cost of the flat fee and cost per minute.
:
Let f = flat fee for the 1st 8 min
Let a = cost for each additional min
:
Two equations:
:
"Sally was there for 12 mins and cost her $5."
a(12-8) + f = $5
4a + f = $5
:
" John was there for 17 mins and cost him $6.25."
a(17-8) + f = $6.25
9a + f = 6.25
:
We can use elimination here, subtract the 1st equation from the 2nd
9a + f = 6.25
4a + f = 5.00
-----------------subtraction eliminates f find a
5a = 1.25
a =
a = .25 for each additional min
:
Find f using the 1st equation
4(.25) + f = 5
1.00 + f = 5
f = 5 - 1
f = $4 is the flat fee for the 1st 8 min
:
Check our solutions in the 2nd equation
9(.25) + 4.00 = 6.25
