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In 70 liters of a mixture of milk and water, the quantity of

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In 70 liters of a mixture of milk and water, the quantity of [#permalink]

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24 Jan 2012, 14:40
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In 70 liters of a mixture of milk and water ,the quantity of water is 10%. how much water should be added so that new mixture may 25% water.
[Reveal] Spoiler:
14

can it solve through chemical mixture strategy in mgmat guide

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24 Jan 2012, 14:51
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Expert's post
TomB wrote:
In 70 liters of a mixture of milk and water ,the quantity of water is 10%. how much water should be added so that new mixture may 25% water.
[Reveal] Spoiler:
14

can it solve through chemical mixture strategy in mgmat guide

Please post answer choices for PS problems. Also make sure you don't reword the questions you post.

As for the question:
There are 10% of water in 70L --> there are 7L of waters;
After x liters of water is added amount of water becomes (7+x) liters, which on the other hand is 1/4th (25%) of new (70+x) liters of mixture: 7+x=1/4*(70+x) --> 28+4x=70+x --> x=14.

Hope it's clear.
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Re: In 70 liters of a mixture of milk and water, the quantity of [#permalink]

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25 Jan 2012, 02:16
70 = 0,1W + 0,9M
Water = 7 Liter

New1: Add x-Liter water to increase W% from 10% to 25%
New2:
7+x = (70+x)1/4
-42/4 = -3/4x
14 = x

You need to add 14 Liter of Water to get a total of 21 Liter of Water in 84Liter of mixture

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Re: In 70 liters of a mixture of milk and water, the quantity of [#permalink]

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25 Jan 2012, 04:36
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TomB wrote:
In 70 liters of a mixture of milk and water ,the quantity of water is 10%. how much water should be added so that new mixture may 25% water.
[Reveal] Spoiler:
14

can it solve through chemical mixture strategy in mgmat guide

Check out how to handle generic mixture questions here:
http://www.veritasprep.com/blog/2011/04 ... -mixtures/

The formula discussed can be used in a ton of questions including this one. Once you get used to this method of solving, you will pretty much be solving this question orally. After going through the post, see if this makes sense:

Solution 1 has 10% water.
Solution 2 has 100% water. (You are mixing solution 1 with pure water.)
Mixture should have 25% water.
w1/w2 = (100 – 25)/(25 – 10) = 75/15 = 5/1
So volume of solution 1 : volume of water = 5:1
Solution 1 is 70 litres, so 14 litres of water must be added.
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Re: In 70 liters of a mixture of milk and water, the quantity of [#permalink]

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25 Jan 2012, 09:15
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my way
now water is 7/70
it will be (7+X)/(70+X) and it shoud =1/4.

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Re: In 70 liters of a mixture of milk and water, the quantity of [#permalink]

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25 Jan 2012, 11:43
first the amount of water was 70*10%=7

(7+x)/(70+x)=1/4
x=14
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Re: In 70 liters of a mixture of milk and water, the quantity of [#permalink]

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26 Jan 2012, 06:25
In 70 ltr solution we have 63 ltr of milk and 7 ltr of water
now we are adding water but the amount of milk remains constant so (70+x)*75/100 = 63 where x is the amount of water added
on solving x=14

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Re: In 70 liters of a mixture of milk and water, the quantity of [#permalink]

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28 Feb 2012, 18:23
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I draw the solution for you (attached). It might help you understand it a bit easier.
Attachments

mixture.png [ 25.98 KiB | Viewed 6032 times ]

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Re: In 70 liters of a mixture of milk and water, the quantity of [#permalink]

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29 Feb 2012, 13:18
(7+x)/(70+x)=1/4
Solve for x; x=14

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Re: In 70 liters of a mixture of milk and water, the quantity of [#permalink]

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15 Apr 2012, 21:44
Karishma,

I solved w1/w2 to be
(90-25)/(25-10) = 65/15.

Can you please explain how you got 75/15?
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Re: In 70 liters of a mixture of milk and water, the quantity of [#permalink]

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17 Apr 2012, 11:44
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Expert's post
ENAFEX wrote:
Karishma,

I solved w1/w2 to be
(90-25)/(25-10) = 65/15.

Can you please explain how you got 75/15?

The two mixtures are: a 10% water solution, only water (which is 100% water)
We combine them to get 25% water solution.
Therefore, it is actually (100 - 25)/(25 - 10) and not (90 - 25)/(25 - 10)
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Re: In 70 liters of a mixture of milk and water, the quantity of [#permalink]

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13 Oct 2013, 15:55
Hello from the GMAT Club BumpBot!

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Re: In 70 liters of a mixture of milk and water, the quantity of [#permalink]

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19 Oct 2013, 23:46
TomB wrote:
In 70 liters of a mixture of milk and water ,the quantity of water is 10%. how much water should be added so that new mixture may 25% water.
[Reveal] Spoiler:
14

can it solve through chemical mixture strategy in mgmat guide

@banuel or @veritasprepkarishma please can you modify this problem to include ans choices.
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Re: In 70 liters of a mixture of milk and water, the quantity of [#permalink]

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20 Oct 2013, 04:11
ankur1901 wrote:
TomB wrote:
In 70 liters of a mixture of milk and water ,the quantity of water is 10%. how much water should be added so that new mixture may 25% water.
[Reveal] Spoiler:
14

can it solve through chemical mixture strategy in mgmat guide

@banuel or @veritasprepkarishma please can you modify this problem to include ans choices.

No answer choices are available for this question.
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Re: In 70 liters of a mixture of milk and water, the quantity of [#permalink]

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15 Dec 2014, 05:27
VeritasPrepKarishma, How can we come to know which problems can be solved using the weighted averages formula..Is it applicable to all mixture problems?Or specific ones?

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Re: In 70 liters of a mixture of milk and water, the quantity of [#permalink]

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15 Dec 2014, 19:59
Ralphcuisak wrote:
VeritasPrepKarishma, How can we come to know which problems can be solved using the weighted averages formula..Is it applicable to all mixture problems?Or specific ones?

For most mixture problems, weighted average formula is quite convenient. Whenever you add two things and consider the final solution or have the final solution and split it into two, weighted averages formula is relevant. For some replacement problems, you need additional theory discussed here: http://www.veritasprep.com/blog/2012/01 ... -mixtures/
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Re: In 70 liters of a mixture of milk and water, the quantity of [#permalink]

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16 Dec 2014, 01:14
Thank you for the response Karishma..Will look into the article and implement it for mixture problems..

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Re: In 70 liters of a mixture of milk and water, the quantity of [#permalink]

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20 Mar 2016, 02:46
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).

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Re: In 70 liters of a mixture of milk and water, the quantity of   [#permalink] 20 Mar 2016, 02:46
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