f r represent the number of days the parking lot is used, which of the following equations could be used to calculate when the options would cost the

[eddy2017]

hi, i was trying to make head or tail of this before going to you, but i am having trouble seeing where something in the equation comes from.

parking fees at the local airport are $9.00 per day. individuals who use the service frequently are given the opportunity to purchase a monthly discount card for 20 dollars. with the discount card, the parking fee is reduced to 5.50 per day. if r represent the number of days the parking lot is used, which of the following equations could be used to calculate when the options would cost the same amount and for how many days the cost will be the same, no matter which option is chosen.
this is the answer:
9r=28+5.50r;(r=8)

here's what has been given
daily fees=9 dollars
discount of 20 dollars a month
with the discount the parking fee is reduced to 5.50 per day( instead of 9 dollars, there is a 3.50 reduction)
r = the number of days the parking lot is used

this is the right answer
9r=28+5.50r;(r=8)
let me try to break it down
9 dollars times the number of days the parking lot is used = 28 ????? where is this coming from? + 5.50 ( reduction of fee cause of discount ); (r=8)
r= 8 because is the result when i simplify the equation given:
9r=28+5.50r
9r-5.50r=28
3.5r=28 divide both sides by 3.5
r=8
but why t he 28 in the equation. WHY?
thanks for you inestimable help,
eddy

 

[JeffM]

I suspect there is a typographical error in the statement of the problem, and it SHOULD SAY that the price of the monthly discount card is $28.

9r = 28 + 5.5r
18r = 56 + 11r
7r = 56
r = 8

 

[eddy2017]

I suspect there is a typographical error in the statement of the problem, and it SHOULD SAY that the price of the monthly discount card is $28.

9r = 28 + 5.5r
18r = 56 + 11r
7r = 56
r = 8

oh, that makes it plain, then. thanks a lot, Jeff!

 

[HallsofIvy]

The other possibility is that the "$20"is correcty and that
"9r= 28+5.5r" should have been "9r= 20+ 5.5r".

 

[lev888]

hi, i was trying to make head or tail of this before going to you, but i am having trouble seeing where something in the equation comes from.

parking fees at the local airport are $9.00 per day. individuals who use the service frequently are given the opportunity to purchase a monthly discount card for 20 dollars. with the discount card, the parking fee is reduced to 5.50 per day. if r represent the number of days the parking lot is used, which of the following equations could be used to calculate when the options would cost the same amount and for how many days the cost will be the same, no matter which option is chosen.
this is the answer:
9r=28+5.50r;(r=8)

here's what has been given
daily fees=9 dollars
discount of 20 dollars a month
with the discount the parking fee is reduced to 5.50 per day( instead of 9 dollars, there is a 3.50 reduction)
r = the number of days the parking lot is used

this is the right answer
9r=28+5.50r;(r=8)
let me try to break it down
9 dollars times the number of days the parking lot is used = 28 ????? where is this coming from? + 5.50 ( reduction of fee cause of discount ); (r=8)
r= 8 because is the result when i simplify the equation given:
9r=28+5.50r
9r-5.50r=28
3.5r=28 divide both sides by 3.5
r=8
but why t he 28 in the equation. WHY?
thanks for you inestimable help,
eddy

I wouldn't use this approach (at least not at first) - look at the answer and try to figure out where its parts are coming from. I would first try to solve the problem myself, maybe ask for a hint here. Get an answer, then compare it to the answer in the book.

 

[Steven G]

Same comment as lev. Why are you looking at the answer and trying to figure out why it is correct. Just solve the problem on your own!