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# During the first 11 months of a recent year, a certain charitable orga

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Re: During the first 11 months of a recent year, a certain charitable orga [#permalink]
eleuth
During the first 11 months of a recent year, a certain charitable organization received an average of $20,600 per month in donations. How much did the organization receive in donations during December of that year if the average amount of donations per month for the entire year was$21,000?

A. $21,400 B.$21,600
C. $24,000 D.$25,400
E. $25,800 Hello There, Average for 11 months = 20,600 M1 + M2 + ……. + M11 ------------------------------- = 20,600 11 M1 + M2 +……..+ M11 = 20,600 X 11 = 2,26,600 Average for 12 months = 21,000 M1 + M2 + ……. + M11 + M12 ----------------------------------------- = 21,000 12 (M1 + M2 +……..+ M11) + M12 = 21,000 X 12 2,26,600 + M12 = 2,52,000 M12 = 2,52,000 – 2,26,600 = 25,400 Tutor Joined: 16 Oct 2010 Posts: 15302 Own Kudos [?]: 68067 [3] Given Kudos: 442 Location: Pune, India During the first 11 months of a recent year, a certain charitable orga [#permalink] 1 Kudos 2 Bookmarks Expert Reply bharatS eleuth During the first 11 months of a recent year, a certain charitable organization received an average of$20,600 per month in donations. How much did the organization receive in donations during December of that year if the average amount of donations per month for the entire year was $21,000? A.$21,400
B. $21,600 C.$24,000
D. $25,400 E.$25,800

Hello There,
Average for 11 months = 20,600
M1 + M2 + ……. + M11
------------------------------- = 20,600
11

M1 + M2 +……..+ M11 = 20,600 X 11 = 2,26,600

Average for 12 months = 21,000
M1 + M2 + ……. + M11 + M12
----------------------------------------- = 21,000
12

(M1 + M2 +……..+ M11) + M12 = 21,000 X 12
2,26,600 + M12 = 2,52,000
M12 = 2,52,000 – 2,26,600 = 25,400

Your method is correct but it involves quite a bit of calculations. The method used by Bunuel above is much more crisp.

Originally posted by KarishmaB on 20 Oct 2014, 20:31.
Last edited by KarishmaB on 17 Oct 2022, 01:06, edited 1 time in total.
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Re: During the first 11 months of a recent year, a certain charitable orga [#permalink]
VeritasPrepKarishma
bharatS
eleuth
During the first 11 months of a recent year, a certain charitable organization received an average of $20,600 per month in donations. How much did the organization receive in donations during December of that year if the average amount of donations per month for the entire year was$21,000?

A. $21,400 B.$21,600
C. $24,000 D.$25,400
E. $25,800 Hello There, Average for 11 months = 20,600 M1 + M2 + ……. + M11 ------------------------------- = 20,600 11 M1 + M2 +……..+ M11 = 20,600 X 11 = 2,26,600 Average for 12 months = 21,000 M1 + M2 + ……. + M11 + M12 ----------------------------------------- = 21,000 12 (M1 + M2 +……..+ M11) + M12 = 21,000 X 12 2,26,600 + M12 = 2,52,000 M12 = 2,52,000 – 2,26,600 = 25,400 Your method is correct but it involves quite a bit of calculations. The method used by Bunuel above is much more crisp. This method is discussed in detail here: https://www.gmatclub.com/forum/veritas-prep-resource-links-no-longer-available-399979.html#/2012/04 ... etic-mean/ Check it out. Hello There, Ya, was just trying to explain the concept. Surely will follow Bunuel. Thanks for your inputs. Senior Manager Joined: 07 Apr 2014 Status:Math is psycho-logical Posts: 331 Own Kudos [?]: 408 [0] Given Kudos: 169 Location: Netherlands GMAT Date: 02-11-2015 WE:Psychology and Counseling (Other) Re: During the first 11 months of a recent year, a certain charitable orga [#permalink] While I like the response by MKS, I also tried to do it another way and it doesn't work out. Could you tell me what I am doing wrong? So, starting by looking for the sum of the earning we have: 20600 = S/11 --> S = 226600 Then if we add the remaining earning for the last month of the year this becomes: 21000 = (226600 + x) / 12 => x = 229400, which is wrong... GMAT Club Legend Joined: 19 Dec 2014 Status:GMAT Assassin/Co-Founder Affiliations: EMPOWERgmat Posts: 21832 Own Kudos [?]: 11868 [1] Given Kudos: 450 Location: United States (CA) GMAT 1: 800 Q51 V49 GRE 1: Q170 V170 Re: During the first 11 months of a recent year, a certain charitable orga [#permalink] 1 Kudos Expert Reply Hi pacifist85, Your set-up and logic are fine. When you get to this point in the "math".... 21000 = (226600 + x) / 12 ....What did you do next? (you include a value for X that was incorrect, so I don't know HOW you worked through your math). Here is a correct series of math "steps": 21,000(12) = 252,000 252,000 = 226,600 + X 25,400 = X Final Answer: GMAT assassins aren't born, they're made, Rich Senior Manager Joined: 07 Apr 2014 Status:Math is psycho-logical Posts: 331 Own Kudos [?]: 408 [0] Given Kudos: 169 Location: Netherlands GMAT Date: 02-11-2015 WE:Psychology and Counseling (Other) Re: During the first 11 months of a recent year, a certain charitable orga [#permalink] Hi Rich, What I did next was to just solve for X: 21000 = (226600 + x) / 12 => x = 229400. So, my reasoning behind this was to add the missing amount to the S ( 226600 + x ) and divide again by 12, because now we have a new day to account for ( / 12 ). And I know see that I actually get the correct answer. As 21000*12=226600+x --> 252000 = 226600 + x --> 252000 - 226600 = x --> x = 25400. At the moment I don't know what my problem was.. Perhaps I shouldn't be GMATing for 12 hours evryday... But, what did you mean with "What did you do next? (you include a value for X that was incorrect, so I don't know HOW you worked through your math)". Why was adding X there incorrect? Thank you! GMAT Club Legend Joined: 19 Dec 2014 Status:GMAT Assassin/Co-Founder Affiliations: EMPOWERgmat Posts: 21832 Own Kudos [?]: 11868 [0] Given Kudos: 450 Location: United States (CA) GMAT 1: 800 Q51 V49 GRE 1: Q170 V170 Re: During the first 11 months of a recent year, a certain charitable orga [#permalink] Expert Reply Hi pacifist85, I was asking about how you did your calculation because you did not include that information. There was just a number (229,400) and a comment stating "...which is wrong." You got to that number somehow, but you did not explain how. Just about every Test Taker makes some silly mistakes during practice; to keep those silly mistakes from happening AGAIN, it's important to define WHY they happened in the first place. Maybe you didn't take enough notes, maybe you did math in your head, maybe you used "math rules" incorrectly. Whatever the reason, by defining it....you should be able to fix it. GMAT assassins aren't born, they're made, Rich Senior Manager Joined: 07 Apr 2014 Status:Math is psycho-logical Posts: 331 Own Kudos [?]: 408 [0] Given Kudos: 169 Location: Netherlands GMAT Date: 02-11-2015 WE:Psychology and Counseling (Other) Re: During the first 11 months of a recent year, a certain charitable orga [#permalink] Thank you Rich. It is true that I make such silly mistakes more often than I should. Be it in mistakes is easy calculations or even copying the figures incorrectly... Not sure what is wrong there. I guess I cannot focus as much as needed! Thank you though, because up until you told me that the solution seems correct (apart from the result of course) I was thinking that I was solving the problem incorrectly. Which was surprising since statistics is one of my strengths! Intern Joined: 23 Sep 2014 Posts: 25 Own Kudos [?]: 102 [0] Given Kudos: 210 Location: India Concentration: Marketing, Finance GMAT 1: 670 Q48 V34 During the first 11 months of a recent year, a certain charitable orga [#permalink] Hi Bunuel VeritasPrepKarishma, I was reviewing the GMATPrep mock I gave today, I scored a Q48 with 7 incorrect, with last 17 Q's correct. This particular question came as Q28( The difficulty level mentioned here is sub 600), and Q27 that came in the mock has a difficulty level of 700+ on GMAT Club, are the GMAT prep test not adaptive? or is the same fluctuation in the difficulty level of the Q can be expected in the Exam? I am a retaker, have Q46 and Q44 in my previous two attempts, so needed to be sure, whether this is an inflated score or pretty much according to my current ability. Exam Pack 1 : GMAT3 (Q48,V37) GMAT4(Q48,V39) TIA Tutor Joined: 16 Oct 2010 Posts: 15302 Own Kudos [?]: 68067 [1] Given Kudos: 442 Location: Pune, India Re: During the first 11 months of a recent year, a certain charitable orga [#permalink] 1 Kudos Expert Reply believer700 Hi Bunuel VeritasPrepKarishma, I was reviewing the GMATPrep mock I gave today, I scored a Q48 with 7 incorrect, with last 17 Q's correct. This particular question came as Q28( The difficulty level mentioned here is sub 600), and Q27 that came in the mock has a difficulty level of 700+ on GMAT Club, are the GMAT prep test not adaptive? or is the same fluctuation in the difficulty level of the Q can be expected in the Exam? I am a retaker, have Q46 and Q44 in my previous two attempts, so needed to be sure, whether this is an inflated score or pretty much according to my current ability. Exam Pack 1 : GMAT3 (Q48,V37) GMAT4(Q48,V39) TIA GMAT Prep is adaptive. Some sudden variation in difficulty level could be there because the algorithm considers various aspects (other than the difficulty level) such as the topics that still need to be tested, the question format to be given etc while selecting the next question. There is no reason for the score to be inflated. Intern Joined: 23 Sep 2014 Posts: 25 Own Kudos [?]: 102 [0] Given Kudos: 210 Location: India Concentration: Marketing, Finance GMAT 1: 670 Q48 V34 Re: During the first 11 months of a recent year, a certain charitable orga [#permalink] VeritasPrepKarishma believer700 Hi Bunuel VeritasPrepKarishma, I was reviewing the GMATPrep mock I gave today, I scored a Q48 with 7 incorrect, with last 17 Q's correct. This particular question came as Q28( The difficulty level mentioned here is sub 600), and Q27 that came in the mock has a difficulty level of 700+ on GMAT Club, are the GMAT prep test not adaptive? or is the same fluctuation in the difficulty level of the Q can be expected in the Exam? I am a retaker, have Q46 and Q44 in my previous two attempts, so needed to be sure, whether this is an inflated score or pretty much according to my current ability. Exam Pack 1 : GMAT3 (Q48,V37) GMAT4(Q48,V39) TIA GMAT Prep is adaptive. Some sudden variation in difficulty level could be there because the algorithm considers various aspects (other than the difficulty level) such as the topics that still need to be tested, the question format to be given etc while selecting the next question. There is no reason for the score to be inflated. This helps a lot. Many thanks Manager Joined: 26 Mar 2017 Posts: 62 Own Kudos [?]: 226 [0] Given Kudos: 1 Re: During the first 11 months of a recent year, a certain charitable orga [#permalink] MKS Say for December month, It is X then $$11*(20600) + X = 12 * (21000)$$ => x = 25400 - Option D well I spent way too much time trying to find a way avoiding the long multiplication Intern Joined: 18 Jan 2017 Posts: 20 Own Kudos [?]: 19 [1] Given Kudos: 171 Re: During the first 11 months of a recent year, a certain charitable orga [#permalink] 1 Kudos jadon During the first 11 months of a recent year, a certain charitable organization received an average of$20,600 per month in donations. How much did the organization receive in donations during December of that year if the average amount of donations per month for the entire year was $21,000? A.$21,400
B. $21,600 C.$24,000
D. $25,400 E.$25,800

average for 11 months = 20,600
20,600= x/11
x=226,600

average for the year= 21,000
21,000=x/12
x=252,000

252,000-226,600= 25,400
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Re: During the first 11 months of a recent year, a certain charitable orga [#permalink]
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During the first 11 months of a recent year, a certain charitable organization received an average of $20,600 per month in donations. How much did the organization receive in donations during December of that year if the average amount of donations per month for the entire year was$21,000?

A. $21,400 B.$21,600
C. $24,000 D.$25,400
E. $25,800 If the average amount of donations was$21,000, we need to make up $400 for each prior month.$400 * 11 + 21,000 = \$4,400 + 21,000 = 25,400

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Re: During the first 11 months of a recent year, a certain charitable orga [#permalink]
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Re: During the first 11 months of a recent year, a certain charitable orga [#permalink]
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