In a certain state, gasoline stations compute the price per gallon "p"

I picked C. I divided the 1.04 with P before subtracting 0.18. What rule is there that I am unaware of here?

Substraction has to be done first, & then the whole term to be divided by 1.04

question stem can be written as p = d + 4% of d +0.18
=> p = d(1+0.04)+0.18
=> p-0.18 = d(1+0.04)
d = p-018 /(1.04)

The problem states "...then adding a gasoline tax of $0.18 per gallon"

So, why is this not P = 1.04d + 0.18d instead of P = 1.04d + 0.18

Please help!

Thanks

Coolfool

Because p in the solutions above is already the price per gallon (the price of ONE gallon). Please re-read the solutions above.

Hope it helps.

Hi All,

This question can be solved by TESTing VALUES.

P = Price per gallon CHARGED
D = Price per gallon for the Dealer

We're told that the Dealer price has a 4% tax AND 18 cents per gallon added on.

So, I'm going to pick a nice round number for D.

D = $10
P = $10 +4%($10) + 18 cents = 10.40 + .18 = 10.58

Now, we plug in D = 10 and P = 10.58 into the answer choices; there's only one answer that matches...

Final Answer:

GMAT assassins aren't born, they're made,
Rich

In a certain state, gasoline stations compute the price per gallon "p", in dollars, charged at the pump by adding a 4 percent sales tax to the dealer's price per gallon "d", in dollars . . .
We can write: p = d + 4% of d
= d + 0.04d
= 1.04d
So, we have: p = 1.04d

. . . and then adding a gasoline tax of $0.18 per gallon.
We get: p = 1.04d + 0.18

Which of the following gives the dealer's price per gallon "d" in terms of the price per gallon "p" charged at the pump?
We need to take p = 1.04d + 0.18 and solve for d

Take: p = 1.04d + 0.18
Subtract 0.18 from both sides to get: p - 0.18 = 1.04d
Divide both sides by 1.04 to get: (p - 0.18)/1.04 = d

Answer: D

Hi
Using this approach, wouldn't there be 2 possible answers (B & D)? Since substituting p = 1.22 into option B gives us d = 1.22/1.22 = 1?

Hi achanak,

Yes, while using TEST IT is a great option for this question, using D = 1 does lead to two answers that 'match' what we're looking for (the correct answer and one of the incorrect ones). This is ultimately why you typically should not 'TEST' the numbers 0 or 1 when dealing with PS questions. Using a slightly larger number (I used D = 10 in my explanation above) will likely lead you to just one matching answer (re: the correct one).

GMAT assassins aren't born, they're made,
Rich

avigutman EMPOWERgmatRichC

I found this bit quite vague: "...by adding a 4 percent sales tax to the dealer's price per gallon "d".. "

How does one deduce that the 4 percent sales tax is 4 percent of the dealer's price per gallon?

From my understanding, sales tax is applied on the final price of the item, so I set the equation up as such:

p = 0.04(p) + d + $0.18

Is there a rule regarding sales tax that I'm unaware of?

Thanks in advance!

This doesn't make any sense, achloes. It would lead to an infinite loop, as the "final price" would keep getting updated every time you add the sales tax. Similarly, you don't calculate your tip at a restaurant based on a price that already includes the tip!
In general, sentences that involve percent will have a preposition and whatever comes right after the preposition is going to be your base (the denominator for the percent).
Some examples, with the prepositions boldfaced:
"30% more than 50" is 65.
"30% of 15" is 4.5.
"Adding 20% to 100" gets you 120.

Hi achloes,

When a GMAT question asks us to 'translate' an equation from written words, the given words are often really specific (to avoid any confusion or ambiguity), so you should work through your translation in small steps. For example, in this prompt, we're told:

"In a certain state, gasoline stations compute the price per gallon "p", in dollars, charged at the pump...."

P = Gas Price per gallon charged at the pump


"... by adding a 4 percent sales tax to the DEALER'S PRICE per gallon "d", in dollars,...."

Here, we're given a 2nd variable ("D"), and this next calculation refers specifically to the Dealer's Price:

P = D + (.04)(D)


"...and then adding a gasoline tax of $0.18 per gallon."

Now we add an additional $0.18 to the total:

P = D + (.04)D + .18

IF you want to continue working through all of this Algebraically, then you're just a few steps away from solving for D.

GMAT assassins aren't born, they're made,
Rich

Contact Rich at: Rich.C@empowergmat.com

Hi BrentGMATPrepNow, following the logic of sales tax (d + 4% of d), not sure why adding a gasoline tax of $0.18 per gallon is not the same format as g + 0.18g but only .018?
How to interpret when is comes to sales tax? As not every country or I never come across that there's sales tax and also gasoline tax for adding petrol? Is this type of knowledge is assumed?
Thanks Brent

What does g represent in your solution?
I can't answer your question until I have this information.

Hi BrentGMATPrepNow, g represent gasoline, so a gasoline tax of $0.18 per gallon is 0.18g? if we follow the same word logic of sales tax here....

Hi Kimberly77,

The prompt gives us the variable "P" as 'price per gallon' - and since we're not actually asked to calculate a total amount of money spent (for example, to fill a 12-gallon gas tank), we DON'T need another variable to represent the number of gallons of gas.

Based on the given information in the prompt, everything we're told is in terms of 'P':

-The dealer price per gallon (D) and the 4% tax on that dealer price (.04D)
-The additional 18 cents per gallon (.18)

So P = D + .04D + .18
P = 1.04D + .18

This is the price per gallon. If we're ever given the value of D, then we can calculate the value of P... For example:

IF....D = $1, then
P = 1.04 + .18 = $1.22 per gallon

GMAT assassins aren't born, they're made,
Rich

Contact Rich at: Rich.C@empowergmat.com

Thanks EMPOWERgmatRichC, think I sort of get it.
d is the variable for 4% sales tax and $0.18 is the gasoline tax in addition to sales tax? Is the understanding correct? Thanks