i doubt....pl explain.

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i doubt....pl explain.

by advita » Fri Nov 19, 2010 5:46 am
232. In a certain state, gasoline stations compute the price per gallon p, in dollars, charged at the pump by adding a 4% sales tax to the dealer's price per gallon d, in dollars, then adding a gasoline tax of $0.18 per gallon. Which of the following gives the dealer's price per gallon d in terms of the price per gallon p charged at the pump?
A) d = p - 0.22
B) d = p/1.22
C) d = (p/1.04) - 0.18
D) d = p - 0.18/1.04
E) d = p - 0.04/1.18

Solution:
[spoiler]The easiest way to start is to set up the equation in terms of d and p in the way the stimulus presents the question:
p = 1.04d + 0.18
Now solve for d:
p - 0.18 = 1.04d
d = (p - 0.18) / 1.04 (D)[/spoiler]

isn't answer should be : B) d = p/1.22
source: 300+ gmat Q.

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by Rahul@gurome » Fri Nov 19, 2010 5:55 am
advita wrote:232. In a certain state, gasoline stations compute the price per gallon p, in dollars, charged at the pump by adding a 4% sales tax to the dealer's price per gallon d, in dollars, then adding a gasoline tax of $0.18 per gallon. Which of the following gives the dealer's price per gallon d in terms of the price per gallon p charged at the pump?
A) d = p - 0.22
B) d = p/1.22
C) d = (p/1.04) - 0.18
D) d = p - 0.18/1.04
E) d = p - 0.04/1.18

Solution:
[spoiler]The easiest way to start is to set up the equation in terms of d and p in the way the stimulus presents the question:
p = 1.04d + 0.18
Now solve for d:
p - 0.18 = 1.04d
d = (p - 0.18) / 1.04 (D)[/spoiler]

isn't answer should be : B) d = p/1.22
source: 300+ gmat Q.
The solution is perfectly alright.
It'd have been easier to help you if you'd have posted your method.

Anyway, as you bold faced $0.18 per gallon and your answer guess contains 1.22 in it, I assume you've added 0.18 with 1.04 and got 1.22. But 1.04 is multiplied with d. You cannot add (1.04d) with 0.18 and get 1.22d! (0.18 is not multiplied with d, it's an independent term.)
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by advita » Fri Nov 19, 2010 11:42 am
thanks rahul....yeah i got it.

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by RikaMueller » Fri Nov 19, 2010 1:01 pm
Can you pls explain how you reached to the answer?
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by Rahul@gurome » Fri Nov 19, 2010 1:37 pm
RikaMueller wrote:Can you pls explain how you reached to the answer?
Price per gallon = Dealer's price + 4% of Dealer's price + 0.18
=> p = d + 4% of d + 0.18
=> p = d + (4/100)*d + 0.18
=> p = d + (0.04)*d + 0.18
=> p = d*(1 + 0.04) + 0.18
=> p = (1.04)d + 0.18
=> p - 0.18 = (1.04)d
=> d = (p - 0.18)/1.04

The correct answer is D.
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by RikaMueller » Sat Nov 20, 2010 12:52 am
Ah ok, I got that. Was confused with the p - 0.22, and thought that this is the right answer.
Thanks :-)