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Due to a sudden 20% increase in price, one is now able to buy 4 gallon

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Manager
Joined: 07 Jun 2017
Posts: 174
Location: India
Concentration: Technology, General Management
GMAT 1: 660 Q46 V38
GPA: 3.6
WE: Information Technology (Computer Software)
Due to a sudden 20% increase in price, one is now able to buy 4 gallon  [#permalink]

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17 Oct 2017, 04:28
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Difficulty:

75% (hard)

Question Stats:

55% (01:53) correct 45% (02:08) wrong based on 86 sessions

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Due to a sudden 20% increase in price, one is now able to buy 4 gallons lesser oil than earlier on the same expenditure of
$600. What is the dollar increase in the price of oil per gallon? A.$2
B. $5 C.$10
D. $20 E.$25

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email: nkmungila@gmail.com
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Due to a sudden 20% increase in price, one is now able to buy 4 gallon  [#permalink]

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17 Oct 2017, 05:14
nkmungila wrote:
Due to a sudden 20% increase in price, one is now able to buy 4 gallons lesser oil than earlier on the same expenditure of
$600. What is the dollar increase in the price of oil per gallon? A.$2
B. $5 C.$10
D. $20 E.$25

Test the answers. The equation for this one was taking too long. Backsolving was quick.

(Price per gallon P) * (# of gallons Q) = Total cost

Q = Total cost/price per gallon

1) Find original price from given dollar increase

2) Find original # of gallons by dividing $600 by old price per gallon 3) Find new price = (1.2)($old), OR
($Old price + added$ increase)

4) Find new # gallons. Divide 600 by new price

Answer C) $10$10 is both the dollar increase in price and a .20 increase of original price, x

Original price:

$10 = .2x = $$\frac{10}{.2} = 50$$ Original number of gallons: $$\frac{600}{50PerGal} = 12$$ gallons New price:$50 + $10 (or 1.2 *$50) = $60 New number of gallons $$\frac{600}{60per} = 10$$ gallons 12 - 10 = 2 fewer gallons now. Too small. That means the dollar price increase is too large. To increase quantity, decrease price. Try B)$5

$5 = .2x Original price: $$\frac{5}{.2} = 25$$ Original quantity: $$\frac{600}{25per} = 24$$ gallons New price: (1.2)($25) or ($25 +$5) = $30 New quantity: $$\frac{600}{30per} = 20$$ gallons 24 - 20 = 4 gallons. Correct Answer B Target Test Prep Representative Status: Founder & CEO Affiliations: Target Test Prep Joined: 14 Oct 2015 Posts: 4170 Location: United States (CA) Re: Due to a sudden 20% increase in price, one is now able to buy 4 gallon [#permalink] Show Tags 19 Oct 2017, 09:16 nkmungila wrote: Due to a sudden 20% increase in price, one is now able to buy 4 gallons lesser oil than earlier on the same expenditure of$600. What is the dollar increase in the price of oil per gallon?

A. $2 B.$5
C. $10 D.$20
E. $25 We can let the original number of gallons of oil = n and the original price = p; thus: np = 600 and (1.2p)(n - 4) = 600 1.2np - 4.8p = 600 Substituting 600 for np in the above equation, we have: 1.2(600) - 4.8p = 600 720 - 4.8p = 600 120 = 4.8p 25 = p The old price was 25, and the new price is 20% more: 25 x 1.2 = 30. Thus, the increase in price is 5 dollars. Answer: B _________________ Scott Woodbury-Stewart Founder and CEO GMAT Quant Self-Study Course 500+ lessons 3000+ practice problems 800+ HD solutions Intern Joined: 16 Jan 2017 Posts: 10 Re: Due to a sudden 20% increase in price, one is now able to buy 4 gallon [#permalink] Show Tags 20 Oct 2018, 11:35 Can we solve this using a logical approach?? Manager Joined: 14 Jun 2018 Posts: 185 Re: Due to a sudden 20% increase in price, one is now able to buy 4 gallon [#permalink] Show Tags 20 Oct 2018, 11:51 3 Let the price of gasoline be x. New Price = 1.2x $$\frac{600}{x} - \frac{600}{1.2x} = 4$$ 120 = 4.8x x = 25 New price = 30 Increase = 5$
Manager
Joined: 14 Jun 2018
Posts: 185
Re: Due to a sudden 20% increase in price, one is now able to buy 4 gallon  [#permalink]

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20 Oct 2018, 12:12
1
castiel wrote:
Can we solve this using a logical approach??

Apart from algebra you could solve it using percentage.

Initial amount = 100
Now price increased by 20% = 120
Since the price increased , you need to decrease consumption by 20/120 * 100 = 16.67% or 1/6 to keep your expenditure the same.

This 16.67% decrease = 4 units of gasoline
Therefore , 100% = 24 units of gasoline
Initial quality = 24 units ; Initial price = 600/24 = 25$Final quantity = 20 units ; Final Price = 600/20 = 30$

Increase = 5\$
Intern
Joined: 16 Jan 2017
Posts: 10
Due to a sudden 20% increase in price, one is now able to buy 4 gallon  [#permalink]

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21 Oct 2018, 00:34
Got it!

Thanks pandeyashwin
Due to a sudden 20% increase in price, one is now able to buy 4 gallon &nbs [#permalink] 21 Oct 2018, 00:34
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Due to a sudden 20% increase in price, one is now able to buy 4 gallon

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