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# For a certain savings account, the table shows the three

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MBA Section Director
Joined: 19 Mar 2012
Posts: 3587
Location: India
GPA: 3.8
WE: Marketing (Energy and Utilities)
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Kudos [?]: 12276 [0], given: 1872

Re: For a certain savings account, the table shows the three [#permalink]

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29 Mar 2013, 08:44
debayan222 wrote:
[
Hey Guys,
I'm sorry but I'm not getting it..
In bank account, if I deposit $1000.00 on say Jan-01 and if for next 30 days there is no transaction then at the end 30 days my bank account will have$ 30000.00 as per your explanations.Does that make sense guys ?Keeping money idle in the bank and its getting multiplied with no. of days kept in the account...I mean certainly there will be addition of Interest but that will not fetch you 30 times your deposit in 30 days.

Then, why we're considering this theory..Bunuel I would request you help.

Please come up with a deep analysis on this.

Its NOT about cash inflow. ITS BECAUSE THE PROMPT MENTIONS THE AVERAGE OF BALANCES
For example
If I have a balance of $1000 for 3 days in my a/c the average is$(1000X3)/3 = 1000

If I had withdrawn $500 on the second day BY THE LOGIC OF THE PROMPT THE AVERAGE WILL BE$(1000+500+500)/3 = $667 Hope its clear _________________ MBA Section Director Joined: 19 Mar 2012 Posts: 3587 Location: India GPA: 3.8 WE: Marketing (Energy and Utilities) Followers: 1562 Kudos [?]: 12276 [1] , given: 1872 Re: For a certain savings account, the table shows the three [#permalink] ### Show Tags 29 Mar 2013, 08:49 1 This post received KUDOS Expert's post Now that the topics are merged my post does not make sense _________________ Intern Joined: 01 Feb 2013 Posts: 10 Location: United States Concentration: Finance, Technology GPA: 3 WE: Analyst (Computer Software) Followers: 0 Kudos [?]: 14 [0], given: 9 Re: For a certain savings account, the table shows the three [#permalink] ### Show Tags 29 Mar 2013, 15:59 Since there is only three things happening on the account...$1000 to start off with, -$350 ($750 left), -$500 ($250 left) how much do we need to deposit to take the avg back to $1000? 1000+750+250 = 2000, divide this by 3 (2000/3) and we get roughly 666. Then$1000 - $666 =$444, so the account must go up to $1000 + 444 =1444 (since 666 is roughly) its 1450 that was deposited on that day. _________________ Goal: 25 KUDOZ and higher scores for everyone! GMAT Club Legend Joined: 09 Sep 2013 Posts: 13934 Followers: 589 Kudos [?]: 167 [0], given: 0 Re: For a certain savings account, the table shows the three [#permalink] ### Show Tags 08 Apr 2014, 03:42 Hello from the GMAT Club BumpBot! Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos). Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email. _________________ Fuqua Thread Master Joined: 28 Nov 2014 Posts: 813 Followers: 12 Kudos [?]: 109 [0], given: 71 Re: For a certain savings account, the table shows the three [#permalink] ### Show Tags 14 Jan 2015, 06:54 I had the same doubt as liarish Thank You Bunuel The explanation was crisp. GMAT Club Legend Joined: 09 Sep 2013 Posts: 13934 Followers: 589 Kudos [?]: 167 [0], given: 0 Re: For a certain savings account, the table shows the three [#permalink] ### Show Tags 18 Feb 2016, 18:42 Hello from the GMAT Club BumpBot! Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos). Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email. _________________ Intern Joined: 20 Jan 2016 Posts: 16 Location: Canada Schools: HBS '18 Followers: 1 Kudos [?]: 0 [0], given: 33 Re: For a certain savings account, the table shows the three [#permalink] ### Show Tags 26 Sep 2016, 12:29 Thanks everyone for the solutions. I was just wondering if there is a faster way to solve this with less number crunching? Veritas Prep GMAT Instructor Joined: 16 Oct 2010 Posts: 7185 Location: Pune, India Followers: 2167 Kudos [?]: 14015 [0], given: 222 Re: For a certain savings account, the table shows the three [#permalink] ### Show Tags 26 Sep 2016, 23:14 anon1 wrote: Attachment: Untitled.png For a certain savings account, the table shows the three transactions for the month of June. The daily balance for the account was recorded at the end of each of the 30 days in June. If the daily balance was$1,000 on June 1 and if the average (arithmetic mean) of the daily balances for June was $1,000, what was the amount of the deposit on June 21? A.$1,000
B. $1,150 C.$1,200
D. $1,450 E.$1,600

[Reveal] Spoiler:
Okay, so june 1 - june 10, the sum of the daily balance in this time period here is 10,000 (because initial balance is 1000, and nothing changes)
june 11-15 - the sum here is 3250 (1000-350)*5
june 15-20 the sum here is 750 (1000-350-500)*5

the sum of all those is 14,000.

Since we want to find a deposit, whose sum makes the total sum of all the balances 30,000 / 30 = 1,000

I did 30,000 - 14,000 which gives me 16,000.

so the sum of the balances for rest of the days (10) must equal 16,000. I do 16,000/10

and that's 1,600. E. But thats wrong. The answer is D

What am I donig wrong here? and what is the false logic?

Responding to a pm: For the ease of calculations, you can use deviation from the mean concept for weighted averages.

Shortfall = Excess
350*20 + 500*15 = 10*x
x = 1450

The concept has been discussed in detail here:
http://www.veritasprep.com/blog/2016/09 ... -averages/
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Re: For a certain savings account, the table shows the three   [#permalink] 26 Sep 2016, 23:14

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