Fresh dates contain 90% water while dry dates contain 28% : GMAT Problem Solving (PS)
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# Fresh dates contain 90% water while dry dates contain 28%

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Fresh dates contain 90% water while dry dates contain 28% [#permalink]

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28 Nov 2012, 09:13
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Fresh dates contain 90% water while dry dates contain 28% water . How many kg of dry dates can be obtained from 36kg of fresh dates ?

A. 5Kg
B. 10Kg
C. 12 Kg
D. 6Kg
[Reveal] Spoiler: OA

Last edited by Bunuel on 28 Nov 2012, 09:19, edited 1 time in total.
Renamed the topic and edited the question.
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Re: Fresh dates contain 90% water while dry dates contain 28% [#permalink]

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28 Nov 2012, 09:30
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prat29 wrote:
Fresh dates contain 90% water while dry dates contain 28% water . How many kg of dry dates can be obtained from 36kg of fresh dates ?

A. 5Kg
B. 10Kg
C. 12 Kg
D. 6Kg

36 kilograms of fresh dates contain 0.1*36=3.6 kilograms of non-water.

Dry dates obtained from these fresh dates will contain the same amount of non-water and we are told that this amount should be 72% of the dry dates, thus x*0.72=3.6 --> x=5 kilograms.

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Hope it helps.
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Re: Fresh dates contain 90% water while dry dates contain 28% [#permalink]

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02 May 2013, 12:42
prat29 wrote:
Fresh dates contain 90% water while dry dates contain 28% water . How many kg of dry dates can be obtained from 36kg of fresh dates ?

A. 5Kg
B. 10Kg
C. 12 Kg
D. 6Kg

I am very much interested to know how this question be done with alligation method ? I tried, but i am missing some elements.

Thanks & Regards
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Re: Fresh dates contain 90% water while dry dates contain 28% [#permalink]

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02 May 2013, 21:03
2
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prat29 wrote:
Fresh dates contain 90% water while dry dates contain 28% water . How many kg of dry dates can be obtained from 36kg of fresh dates ?

A. 5Kg
B. 10Kg
C. 12 Kg
D. 6Kg

Given information can be rephrased as " Fresh dates contain 10% fruit while dry dates contain 72% fruit"

Hence 36 Kg of fresh dates contain 10% of 36 = 3.6 Kg of fruit.
This same amount of fruit is present after the dates are dried.
If we assume the mass of the dry dates obtained as x Kg, then 72% of x = 3.6
$$0.72*x = 3.6$$
Hence x = 5 Kg
Option A is the correct answer
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Re: Fresh dates contain 90% water while dry dates contain 28% [#permalink]

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03 May 2013, 05:09
3
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Expert's post
prat29 wrote:
Fresh dates contain 90% water while dry dates contain 28% water . How many kg of dry dates can be obtained from 36kg of fresh dates ?

A. 5Kg
B. 10Kg
C. 12 Kg
D. 6Kg

Responding to a pm:

Personally, I would use the method used by Bunuel above. But if you insist on using the "alligation method" which we call "scale method", here is how you can do it:

What two things are mixed to give the third?
Dry dates are mixed with water to give fresh dates.

Dry dates have 28% water, water is 100% water and fresh dates have 90% water.

Dry dates/water = w1/w2 = (A2 - Aavg)/(Aavg - A1) = (100 - 90)/(90 - 28) = 10/62 = 5/31
Mixing 5 kg of dry dates with 31 kg (to maintain consistency) of water will give you 36 kg of fresh dates.

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Get started with Veritas Prep GMAT On Demand for $199 Veritas Prep Reviews Intern Joined: 07 Oct 2012 Posts: 23 Location: India Concentration: General Management, Finance GMAT 1: 640 Q45 V33 WE: Engineering (Other) Followers: 0 Kudos [?]: 11 [1] , given: 7 Re: Fresh dates contain 90% water while dry dates contain 28% [#permalink] ### Show Tags 14 Jul 2013, 00:02 1 This post received KUDOS Fresh dates 36 kg = 90% water and 10% pure dates part. So pure dates part= 36 *0.1= 3.6 kg pure date. Dry dates say x kg = 28% water and 72% pure dates part. So pure dates part= x *0.72= 0.72x kg pure date. Equate the pure dates part only, since that quantity is same in both mixture,so 0.72 x = 3.6 x= 3.6/0.72 = 360/72 = 5 kg. Ans A Intern Joined: 31 May 2013 Posts: 17 Followers: 0 Kudos [?]: 0 [0], given: 8 Re: Fresh dates contain 90% water while dry dates contain 28% [#permalink] ### Show Tags 21 Jul 2013, 00:59 why can't i resolve this problem by putting together these 2 equations: 1 F=0.9W 2 D=0.28W D= (0.28F)/0.9 i don't understand what is my error Math Expert Joined: 02 Sep 2009 Posts: 36509 Followers: 7063 Kudos [?]: 92881 [1] , given: 10528 Re: Fresh dates contain 90% water while dry dates contain 28% [#permalink] ### Show Tags 21 Jul 2013, 01:49 1 This post received KUDOS Expert's post lucasITA wrote: why can't i resolve this problem by putting together these 2 equations: 1 F=0.9W 2 D=0.28W D= (0.28F)/0.9 i don't understand what is my error Because both equations are wrong. Should be: W=F*0.1 --> W=36*0.1=3.6 kilograms. W=D*0.72 --> 3.6=D*0.72 --> D=5 kilograms. For more check here: fresh-dates-contain-90-water-while-dry-dates-contain-143245.html#p1148409 and here: fresh-dates-contain-90-water-while-dry-dates-contain-143245.html#p1220200 Hope it helps. _________________ Senior Manager Joined: 17 Dec 2012 Posts: 447 Location: India Followers: 26 Kudos [?]: 395 [0], given: 14 Re: Fresh dates contain 90% water while dry dates contain 28% [#permalink] ### Show Tags 21 Jul 2013, 02:34 prat29 wrote: Fresh dates contain 90% water while dry dates contain 28% water . How many kg of dry dates can be obtained from 36kg of fresh dates ? A. 5Kg B. 10Kg C. 12 Kg D. 6Kg 1. Non-water percentage of fresh grapes and dry grapes are 10% and 72% resp i.e., 7.2 times more in the dry grapes 2. So from 36 kg fresh grapes we can obtain 36/7.2 = 5 kg of dry grapes. _________________ Srinivasan Vaidyaraman Sravna http://www.sravnatestprep.com Classroom and Online Coaching Intern Joined: 29 Sep 2012 Posts: 4 Followers: 0 Kudos [?]: 5 [0], given: 111 Re: Fresh dates contain 90% water while dry dates contain 28% [#permalink] ### Show Tags 23 Jul 2014, 08:53 prat29 wrote: Fresh dates contain 90% water while dry dates contain 28% water . How many kg of dry dates can be obtained from 36kg of fresh dates ? A. 5Kg B. 10Kg C. 12 Kg D. 6Kg Just wanted to chip in my 2 cents for the question… Since a fresh date is 10% non-water and a dry date is 72% non-water then the ratio of non-water for the dry date to the non-water for the fresh date is 10/72 or 5/36. Meaning that for every 36 units of non-water in a fresh date there is 5 units of non-water in the dry date. Hence A Senior Manager Joined: 17 Dec 2012 Posts: 447 Location: India Followers: 26 Kudos [?]: 395 [0], given: 14 Re: Fresh dates contain 90% water while dry dates contain 28% [#permalink] ### Show Tags 23 Jul 2014, 21:32 Weight of elements in 36 kg (fresh dates) water=32.4 kg, other- 3.6 kg To make dry dates out of it some water has to be removed . Let it be x. Weight (dry dates) water = 32.4 -x, other - 3.6 kg Proportion of elements(dry dates) water = 28, other -72 (32.4 -x) / 3.6 = 28/72 From which we can find weight of water to be 1.4 kg and therefore total weight of dry dates = 5 kg. _________________ Srinivasan Vaidyaraman Sravna http://www.sravnatestprep.com Classroom and Online Coaching Intern Joined: 13 Feb 2014 Posts: 1 Schools: AGSM '15 Followers: 0 Kudos [?]: 0 [0], given: 14 Re: Fresh dates contain 90% water while dry dates contain 28% [#permalink] ### Show Tags 18 Jun 2015, 22:54 prat29 wrote: Fresh dates contain 90% water while dry dates contain 28% water . How many kg of dry dates can be obtained from 36kg of fresh dates ? A. 5Kg B. 10Kg C. 12 Kg D. 6Kg fresh date -90% water 10% no water Dry date -28% water 72% no water need to find weight of fry dates from 36 fresh grapes=let it be x constant is non water portion 36 * 10%=72%x x=5kg Intern Status: Active Joined: 11 Sep 2010 Posts: 4 Location: United States Concentration: General Management, Technology WE: Information Technology (Health Care) Followers: 0 Kudos [?]: 0 [0], given: 96 Re: Fresh dates contain 90% water while dry dates contain 28% [#permalink] ### Show Tags 04 Jul 2015, 16:16 1 This post was BOOKMARKED Hi, I tried solving the other way round i.e by equating % of water amount. 0.9 * 36 = 0.28 * d. This doesn't result in 5 kg weight. Why wouldn't this work? Please clarify. Veritas Prep GMAT Instructor Joined: 16 Oct 2010 Posts: 7118 Location: Pune, India Followers: 2128 Kudos [?]: 13619 [0], given: 222 Fresh dates contain 90% water while dry dates contain 28% [#permalink] ### Show Tags 09 Jul 2015, 21:24 ashtitude wrote: Hi, I tried solving the other way round i.e by equating % of water amount. 0.9 * 36 = 0.28 * d. This doesn't result in 5 kg weight. Why wouldn't this work? Please clarify. You cannot equate these two because the amount of water is not equal in these two cases. You get dry dates by removing water from fresh dates. _________________ Karishma Veritas Prep | GMAT Instructor My Blog Get started with Veritas Prep GMAT On Demand for$199

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Re: Fresh dates contain 90% water while dry dates contain 28% [#permalink]

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08 Aug 2015, 09:22
VeritasPrepKarishma wrote:
ashtitude wrote:
Hi,

I tried solving the other way round i.e by equating % of water amount.

0.9 * 36 = 0.28 * d. This doesn't result in 5 kg weight. Why wouldn't this work? Please clarify.

You cannot equate these two because the amount of water is not equal in these two cases. You get dry dates by removing water from fresh dates.

I have the same problem. Can't we divide the total amount of water in 36 kgs across to get the dried grapes?
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Re: Fresh dates contain 90% water while dry dates contain 28% [#permalink]

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26 Sep 2015, 05:10
dry substance in fresh date:

(10/100)*36=3.6kg

3.6kg = 72%
xkg =100%

x=(3.6*100)/72, x=5kg

A
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Re: Fresh dates contain 90% water while dry dates contain 28% [#permalink]

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21 Feb 2016, 00:05
weight * concentration = constant

w1*c1 = w2*c2

36 * 10/100 = w2 * 72/100

w2 = 5 kg.
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Re: Fresh dates contain 90% water while dry dates contain 28%   [#permalink] 21 Feb 2016, 00:05
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