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a bookstore sells new books for $15 each and used books for  Question banks Downloads My Bookmarks Reviews Important topics Author Message TAGS: CEO Joined: 21 Jan 2007 Posts: 2764 Location: New York City Followers: 9 Kudos [?]: 347 [0], given: 4 a bookstore sells new books for$15 each and used books for [#permalink]  22 Oct 2007, 09:15
a bookstore sells new books for $15 each and used books for$10 each.

On every new book, the store makes a profit of $5 while on every used book, it makes a profit of$2.

If on a given day the sales were $125, which of the following cannot be the profit on that day? 27 31 35 39 41 Senior Manager Joined: 02 Aug 2007 Posts: 347 Location: Greater New York City area Schools: Tuck, Ross (R1), Duke, Tepper, ISB (R2), Kenan Flagler (R2) Followers: 3 Kudos [?]: 29 [0], given: 0 [#permalink] 22 Oct 2007, 10:08 E. From the given information about sales, 15x + 10y =125. So, 3x + 2y = 25 Also, from the given information about profits 5x + 2y = 27 or 31 or 25 or 39 or 41. Lets take the first case : 5x + 2y = 27. Solve this and the earlier sales eqn, we get x = 1, y = 11. The values of x and y fit well in to both the equations. Test this for each of the 5 possibilities of value of profit. Its fits for each except for 5x + 2y = 41. If we solve this and sales eqn, we get x = 8. But if we substitute, x = 8 in either of the eqn. y is not an integer. So the answer is E. Whats the OA ? Manager Joined: 18 Jun 2007 Posts: 55 Followers: 1 Kudos [?]: 1 [0], given: 0 [#permalink] 22 Oct 2007, 10:20 15x + 10y = 125 Max profit is when you sell max of X. So, max x = 7. 7*15= 105 + 10y = 125, y =2 Thus, max profit is 7*5 + 2*2 = 39. It can't be higher than 39, so 41 is impossible. Director Joined: 20 Aug 2007 Posts: 852 Location: Chicago Schools: Chicago Booth 2011 Followers: 11 Kudos [?]: 87 [0], given: 1 [#permalink] 22 Oct 2007, 11:04 I get 41 profit is impossible as well. N = new books sold U = used books sold P = profit 15N + 10U = 125 5N + 2U = P combining equations (mult bottom eq by -3) 4U = 125-3P ----------> 125 - 4U = 3P By pluggin in numbers, if you try 41 for P you get 125 - 4U = 122, which is impossible. CEO Joined: 21 Jan 2007 Posts: 2764 Location: New York City Followers: 9 Kudos [?]: 347 [0], given: 4 [#permalink] 06 Dec 2007, 06:09 ben928 wrote: 15x + 10y = 125 Max profit is when you sell max of X. So, max x = 7. 7*15= 105 + 10y = 125, y =2 Thus, max profit is 7*5 + 2*2 = 39. It can't be higher than 39, so 41 is impossible. Excellent approach OA is E. [#permalink] 06 Dec 2007, 06:09 Similar topics Replies Last post Similar Topics: 5 A bookstore that sells used books sells each of its paperbac 7 23 Feb 2014, 06:48 3 The only way that bookstores can profitably sell books at 5 11 Sep 2012, 20:22 selling new/used books for gmat IN INDIA BY TOPPERS 1 05 Jun 2011, 07:09 2 A bookstore sells new books for$15 each and used books for 13 21 Aug 2010, 21:52
The only way that bookstores can profitably sell books at 4 28 Apr 2009, 11:16
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