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Joined: 08 Sep 2017
Posts: 77
Location: Colombia
GMAT 1: 710 Q49 V39 In a certain clothing store, the most expensive pair of socks sells fo  [#permalink]

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Difficulty:   95% (hard)

Question Stats: 51% (02:58) correct 49% (03:10) wrong based on 71 sessions

In a certain clothing store, the most expensive pair of socks sells for one dollar less than twice the price of the cheapest pair of socks. A customer notices that for exactly $18, she can buy three fewer pairs of the most expensive socks than the cheapest socks. What could be the number of pairs of the cheapest socks she could have purchased? (A) 3 (B) 5 (C) 6 (D) 12 (E) 36 _________________ Kudos please if you liked my post Thanks! RC Moderator V Joined: 24 Aug 2016 Posts: 804 Location: Canada Concentration: Entrepreneurship, Operations GMAT 1: 630 Q48 V28 GMAT 2: 540 Q49 V16 Re: In a certain clothing store, the most expensive pair of socks sells fo [#permalink] Show Tags 1 3 dimmak wrote: In a certain clothing store, the most expensive pair of socks sells for one dollar less than twice the price of the cheapest pair of socks. A customer notices that for exactly$18, she can buy three fewer pairs of the most expensive socks than the cheapest socks. What could be the number of pairs of the cheapest socks she could have purchased?

(A) 3
(B) 5
(C) 6
(D) 12
(E) 36

Let the Price of Cheapest pair is x . Hence price of expensive pair is 2x-1
For $18 , we get n cheapest pair & N expensive pair . Hence , n=18/x & N=18/(2x-1) As per the Q steam : $$n-N=3$$ i.e., 18/x - 18/(2x-1) =3 or, 6/x - 6/(2x-1) =1 or , $$6(2x-1)-6x=x(2x-1)$$ or ,$$2x^2 - 7x +6 =0$$ or, $$(2x-3)(x-2)=0$$ =====> $$x=2,1.5$$ When x=2, 2x-1=3 , n=9 & N=6 When x=1.5, 2x-1=2 , n=12 & N=9.......................Hence the ans is 12 (D) _________________ Please let me know if I am going in wrong direction. Thanks in appreciation. CEO  V Joined: 12 Sep 2015 Posts: 3783 Location: Canada Re: In a certain clothing store, the most expensive pair of socks sells fo [#permalink] Show Tags 1 Top Contributor dimmak wrote: In a certain clothing store, the most expensive pair of socks sells for one dollar less than twice the price of the cheapest pair of socks. A customer notices that for exactly$18, she can buy three fewer pairs of the most expensive socks than the cheapest socks. What could be the number of pairs of the cheapest socks she could have purchased?

(A) 3
(B) 5
(C) 6
(D) 12
(E) 36

Let C = price of one pair of the CHEAPEST socks
So, 2C - 1 = price of one pair of the MOST EXPENSIVE socks

A customer notices that for exactly $18, she can buy three fewer pairs of the most expensive socks than the cheapest socks. As a word equation, we can write: (# of pairs of EXPENSIVE socks purchased with$18) = (# of pairs of CHEAP socks purchased with $18) - 3 With$18, the number of pairs of CHEAP socks we can purchase = 18/C
With $18, the number of pairs of EXPENSIVE socks we can purchase = 18/(2C - 1) So, we can write: (18/(2C - 1)) = (18/C) - 3 Multiply both sides by C to get: 18C/(2C - 1) = 18 - 3C Multiply both sides by (2C - 1) to get: 18C = 18(2C - 1) - 3C(2C - 1) Simplify: 18C = 36C - 18 - 6C² + 3C Simplify: 18C = 39C - 18 - 6C² Rearrange to get: 6C² - 21C + 18 = 0 Divide both sides by 3 to get: 2C² - 7C + 6 = 0 Factor to get: (2C - 3)(C - 2) = 0 So, EITHER 2C - 3 = 0 OR C - 2 = 0 In other words, EITHER C = 1.5 OR C = 2 Let's check each answer choice. If C =$1.5 (the price of one pair of the CHEAPEST socks), then 2C - 1 = $2 (the price of one pair of the MOST EXPENSIVE socks) So, the number of CHEAP socks purchased for$18 = 18/$1.5 = 12 And the number of EXPENSIVE socks purchased for$18 = 18/$2 = 9 Perfect, this meets the condition that the customer can buy three fewer pairs of the most expensive socks than the cheapest socks. If C =$2 (the price of one pair of the CHEAPEST socks), then 2C - 1 = $3 (the price of one pair of the MOST EXPENSIVE socks) So, the number of CHEAP socks purchased for$18 = 18/$2 = 9 And the number of EXPENSIVE socks purchased for$18 = 18/$3 = 6 This ALSO meets the condition that the customer can buy three fewer pairs of the most expensive socks than the cheapest socks. So, the customer bought EITHER 12 pairs of cheap socks or 9 pairs of cheap socks. Check the answer choices, we have 12 Answer: D Cheers, Brent _________________ Senior Manager  G Joined: 04 Aug 2010 Posts: 420 Schools: Dartmouth College In a certain clothing store, the most expensive pair of socks sells fo [#permalink] Show Tags 2 dimmak wrote: In a certain clothing store, the most expensive pair of socks sells for one dollar less than twice the price of the cheapest pair of socks. A customer notices that for exactly$18, she can buy three fewer pairs of the most expensive socks than the cheapest socks. What could be the number of pairs of the cheapest socks she could have purchased?

(A) 3
(B) 5
(C) 6
(D) 12
(E) 36

We can PLUG IN THE ANSWERS, which represent the number of cheap pairs that can be purchased for $18. When the correct answer is plugged in, the number of expensive pairs that can be purchased will be 3 less than the number of cheap pairs that can be purchased. B will yield an ugly price for each cheap pair (18/5 = 3.60) and thus is unlikely to be correct. D: 12 pairs, implying that the price for each cheap pair = 18/12 =$1.50
Since each expensive pair costs $1 less than twice each cheap pair, each expensive pair = 2(1.50) - 1 = 2. Number of$2 expensive pairs that be purchased for $18 = 18/2 = 9. Success! The value in blue is 3 less than the value in red. . _________________ GMAT and GRE Tutor Over 1800 followers GMATGuruNY@gmail.com New York, NY If you find one of my posts helpful, please take a moment to click on the "Kudos" icon. Available for tutoring in NYC and long-distance. For more information, please email me at GMATGuruNY@gmail.com. Target Test Prep Representative D Status: Founder & CEO Affiliations: Target Test Prep Joined: 14 Oct 2015 Posts: 6567 Location: United States (CA) Re: In a certain clothing store, the most expensive pair of socks sells fo [#permalink] Show Tags dimmak wrote: In a certain clothing store, the most expensive pair of socks sells for one dollar less than twice the price of the cheapest pair of socks. A customer notices that for exactly$18, she can buy three fewer pairs of the most expensive socks than the cheapest socks. What could be the number of pairs of the cheapest socks she could have purchased?

(A) 3
(B) 5
(C) 6
(D) 12
(E) 36

We can let c = the price of the cheapest socks and e = the price of the expensive socks, and thus:

e = 2c - 1

Letting n = the number of pairs of the cheapest socks that she could buy, we have:

nc = 18

and

(n - 3)e = 18

Equating the second and the third equations, we have:

nc = (n - 3)e

nc = (n - 3)(2c - 1)

nc = 2nc - n - 6c + 3

18 = 2(18) - n - 6(18/n) + 3

18 = 36 - n - 108/n + 3

n - 21 + 108/n = 0

n^2 - 21n + 108 = 0

(n - 9)(n - 12) = 0

n = 9 or n = 12

We see that n is either 12 or 9, but since only 12 is one of the answer choices. 12 is the correct answer.

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If you find one of my posts helpful, please take a moment to click on the "Kudos" button. Re: In a certain clothing store, the most expensive pair of socks sells fo   [#permalink] 04 Mar 2019, 20:13
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