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word problem kaplan word problem

by resilient » Sat Apr 05, 2008 7:16 pm
Tried picking numbers and made complete sense but couldnt find my target answer. MY chosen numbers were G=4, S=10 and D = 1/2 target answer is 25 but couldn't find the answer.

At a certain gas station, gasoline costs G dollars per gallon. A soda from mini mart costs S dollars and when purchasing a soda, a customer receive a discount of d percent on gasoline. What is the total cost, in dollars, of 10 gallons of gas and 1 soda?

a.10g+S
b.DG/100+S
c.dgs/100
d.10g-(dgs-10)
e.10g-(dg/10)+s

qa is E


Generally I am pretty good at these questions. BUt this one, I couldnt find my target in the choice!
Appetite for 700 and I scraped my plate!
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Re: word problem kaplan word problem

by Stuart@KaplanGMAT » Sat Apr 05, 2008 7:51 pm
Enginpasa1 wrote:Tried picking numbers and made complete sense but couldnt find my target answer. MY chosen numbers were G=4, S=10 and D = 1/2 target answer is 25 but couldn't find the answer.

At a certain gas station, gasoline costs G dollars per gallon. A soda from mini mart costs S dollars and when purchasing a soda, a customer receive a discount of d percent on gasoline. What is the total cost, in dollars, of 10 gallons of gas and 1 soda?

a.10g+S
b.DG/100+S
c.dgs/100
d.10g-(dgs-10)
e.10g-(dg/10)+s

qa is E


Generally I am pretty good at these questions. BUt this one, I couldnt find my target in the choice!
The first problem is that you chose d = 1/2 which means a .5% discount - you probably meant to pick d=50 for a 50% discount.

Using values of G=4, s=10 and d=50:

cost for the gas before discount is 4*10 = $40. Apply the 50% discount and the cost of the gas becomes $20.

cost for the soda is $10 - there's no discount on the soda (this might be the second place you made a mistake).

Total cost = $20 + $10 = $30

(e) works out to 10(4) - (50)(4)/10 + 10 = 40 - 200/10 + 10 = 40 - 20 + 10 = 30.. bingo!
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by mmukher » Sat Apr 05, 2008 8:51 pm
Algebraic solution :

Cost of 1 gallon = G
Cost of 10 gallons = 10G
After discount d% = 10G [ (100-d)/100 ] ... = 10G - DG/10

Total cost of discounted gas + 1 soda = 10G - DG/10 + S
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ok

by resilient » Sun Apr 06, 2008 12:51 am
I figured out wht I was doing wrong. I calculated the correct choice wrong and it threw me off. THis made me second guess my the 50 for discount so I made it into a fraction to see if it fit also. I was gettting a bit too analytical.

Thanks Stuart!
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