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100 points for $49 worth of Veritas practice GMATs FREE VERITAS PRACTICE GMAT EXAMS Earn 10 Points Per Post Earn 10 Points Per Thanks Earn 10 Points Per Upvote ## DS - Stats ##### This topic has expert replies Senior | Next Rank: 100 Posts Posts: 54 Joined: 22 Oct 2007 Thanked: 1 times ### DS - Stats by oks » Mon Sep 15, 2008 11:05 am How many more first-time jobless claims were filed in week P than in week T? 1) for weeks P, Q, R, and S, the avg number of first-time jobless claims filed was 388,250 2) for weeks Q, R, S, and T, the avg number of first-time jobless claims filed was 383,000 Answ: C Please explain. Thanks!!! Senior | Next Rank: 100 Posts Posts: 55 Joined: 14 Sep 2008 Location: Netherlands Thanked: 10 times GMAT Score:680 by tendays2go » Mon Sep 15, 2008 12:15 pm Yes, C is the soln. (i) => P+Q+R+S = (388,250 * 4) (ii) => Q+R+S+T= (383,000 * 4) Now, we have to find P-T which is equal to: [P+Q+R+S] - [Q+R+S+T] = (388,250 - 383,000) *4 Hence both the choices combined yield the required value Legendary Member Posts: 683 Joined: 22 Jul 2008 Location: Dubai Thanked: 73 times Followed by:2 members by mals24 » Mon Sep 15, 2008 12:17 pm we need to find the value of P-T St 1 tells us P+Q+R+S = 388250*4 P = 388250*4-Q-R-S But since it doesnt tell us anything about T its INSUFF St 2 tells us Q+R+S+T = 383000*4 T=383000*4-Q-R-S but since it doesnt tell us anything about P its INSUFF Combining them we get P = 388250*4-Q-R-S T=383000*4-Q-R-S Subtract the two statements we get P-T = (388250*4)-(383000*4) Hence the answer is C Master | Next Rank: 500 Posts Posts: 132 Joined: 07 Oct 2008 Thanked: 4 times ### Average by vladmire » Sun Dec 07, 2008 6:10 am If we are trying to find the difference in the number of jobless claims between the 2 weeks why do we multiply 4? I thought P+Q+R+S/4 gave us$388,250 so whats the point in multiplying 4

(388,250 - 383,000) *4 to yield the required value?

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### Re: Average

by Stuart@KaplanGMAT » Sun Dec 07, 2008 7:10 am
vladmire wrote:If we are trying to find the difference in the number of jobless claims between the 2 weeks why do we multiply 4? I thought P+Q+R+S/4 gave us $388,250 so whats the point in multiplying 4 (388,250 - 383,000) *4 to yield the required value? First thing to note is this is DS, so we don't need to actually calcuate. As soon as you see you have enough info, you're done. On this particular question, as long as you know the average formula, you should reach (C) very quickly by combining the two equations you get. If we actually wanted to solve, we need to multiply by 4 precisely because of the equation you provided. (P+Q+R+S)/4 = 388250 (Q+R+S+T)/4 = 383000 Rearranging to make it easier to get the relationship (P-T) that we want: P+Q+R+S = 4(388250) T+Q+R+S = 4(383000) Subtracting the second equation from the first: P-T = 4(388250) - 4(383000) P-T = 4(388250 - 383000) P-T = 4(5250) P-T = 21000 We could have just multiplied both big numbers by 4 before doing the subtraction, but it's much easier to do the arithmetic with smaller numbers. Stuart Kovinsky | Kaplan GMAT Faculty | Toronto Kaplan Exclusive: The Official Test Day Experience | Ready to Take a Free Practice Test? | Kaplan/Beat the GMAT Member Discount BTG100 for$100 off a full course

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