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A mixture of 40 liters of milk and water contains 10% water.

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A mixture of 40 liters of milk and water contains 10% water.  [#permalink]

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New post Updated on: 04 Jul 2018, 06:18
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A mixture of 40 liters of milk and water contains 10% water. how much water should be added to this so that water may be 20% in the new mixture?

A. 4
B. 5
C. 6
D. 7
E. 8

Originally posted by munia123 on 27 Oct 2010, 12:57.
Last edited by abhimahna on 04 Jul 2018, 06:18, edited 1 time in total.
Edited the question and added OA
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Re: A mixture of 40 liters of milk and water contains 10% water.  [#permalink]

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New post 27 Oct 2010, 17:44
1
5
munia123 wrote:
hey guys, i have got another problem. please help me to solve it.the problem says,

a mixture of 40 liters of milk and water contains 10% water. how much water should be added to this so that water may be 20% in the new mixture?

my answer is 4 liter but, i am not sure. please help me.


Please read and follow: how-to-improve-the-forum-search-function-for-others-99451.html

So please:
Provide answer choices for PS questions.

Let the amount of water to be added be \(x\) liters.

We want the percentage of water to increase from 10% to 20% or percentage of non-water to decrease from 90% to 80%. Note that when we add \(x\) liters of water the amount of non-water in mixture in liters remains the same, so:

\(0.9*40=0.8(40+x)\) --> \(x=5\).

Or, the amount of water after adding \(x\) liters of water (\(0.2*(40+x)\)) should be equal to initial amount of water (\(0.1*40\)) plus the amount of water we add (\(x\))

\(0.2*(40+x)=0.1*40+x\) --> \(x=5\).

Hope it helps.
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Re: A mixture of 40 liters of milk and water contains 10% water.  [#permalink]

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New post 27 Oct 2010, 13:33
40 liters of mixture contains 4 liters of water (10%). So, it has 36 liters of milk.

if 36 liters <-> 80%,
100% <-> (36/80)x100 = 45 liters

So, the total water in the mixture should be 9 liters. Since there is already 4 liters in the mixture, 5 liters need to be added.
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Re: A mixture of 40 liters of milk and water contains 10% water.  [#permalink]

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New post 28 Oct 2010, 02:42
Bunuel wrote:
munia123 wrote:
hey guys, i have got another problem. please help me to solve it.the problem says,

a mixture of 40 liters of milk and water contains 10% water. how much water should be added to this so that water may be 20% in the new mixture?

my answer is 4 liter but, i am not sure. please help me.


Please read and follow: how-to-improve-the-forum-search-function-for-others-99451.html

So please:
Provide answer choices for PS questions.

Let the amount of water to be added be \(x\) liters.

We want the percentage of water to increase from 10% to 20% or percentage of non-water to decrease from 90% to 80%. Note that when we add \(x\) liters of water the amount of non-water in mixture in liters remains the same, so:

\(0.9*40=0.8(40+x)\) --> \(x=5\).

Or, the amount of water after adding \(x\) liters of water (\(0.2*(40+x)\)) should be equal to initial amount of water (\(0.1*40\)) plus the amount of water we add (\(x\))

\(0.2*(40+x)=0.1*40+x\) --> \(x=5\).

Hope it helps.




Hi Bunuel, i got the different ans.. let me know where i m wrong....

Problem again :
a mixture of 40 liters of milk and water contains 10% water. how much water should be added to this so that water may be 20% in the new mixture?

a mixture of 40 ltrs water + milk contains 10% of water so 4 ltrs are water rest 36 ltrs are milk.

if i want to make water 20% in the mixture
40*20% = (4+ x) here x is the water to be added to the mixture

so, i got x as 4

please suggest me if i gone wrong???





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Re: A mixture of 40 liters of milk and water contains 10% water.  [#permalink]

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New post 28 Oct 2010, 02:56
vitamingmat wrote:
Bunuel wrote:
munia123 wrote:
hey guys, i have got another problem. please help me to solve it.the problem says,

a mixture of 40 liters of milk and water contains 10% water. how much water should be added to this so that water may be 20% in the new mixture?

my answer is 4 liter but, i am not sure. please help me.


Please read and follow: how-to-improve-the-forum-search-function-for-others-99451.html

So please:
Provide answer choices for PS questions.

Let the amount of water to be added be \(x\) liters.

We want the percentage of water to increase from 10% to 20% or percentage of non-water to decrease from 90% to 80%. Note that when we add \(x\) liters of water the amount of non-water in mixture in liters remains the same, so:

\(0.9*40=0.8(40+x)\) --> \(x=5\).

Or, the amount of water after adding \(x\) liters of water (\(0.2*(40+x)\)) should be equal to initial amount of water (\(0.1*40\)) plus the amount of water we add (\(x\))

\(0.2*(40+x)=0.1*40+x\) --> \(x=5\).

Hope it helps.

Hi Bunuel, i got the different ans.. let me know where i m wrong....

Problem again :
a mixture of 40 liters of milk and water contains 10% water. how much water should be added to this so that water may be 20% in the new mixture?

a mixture of 40 ltrs water + milk contains 10% of water so 4 ltrs are water rest 36 ltrs are milk.

if i want to make water 20% in the mixture
40*20% = (4+ x) here x is the water to be added to the mixture

so, i got x as 4

please suggest me if i gone wrong???


4+x liters of water is 20% of 40+x liters of mixture not 40.
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Re: A mixture of 40 liters of milk and water contains 10% water.  [#permalink]

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New post 28 Oct 2010, 04:06
thanks to bunuel and also thanks to that person who asked the question to bunnel ( i also thought that 40*20% = 40+x). now i have understood. thanks .
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Re: A mixture of 40 liters of milk and water contains 10% water.  [#permalink]

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New post 19 Apr 2014, 00:34
1
No need to complicate much.

4 ltr - Water
36 ltr - milk

Let X water be added then the new mixture must have 20% water

Then

4 + X = 20/100 (40+X)

X=5
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Re: A mixture of 40 liters of milk and water contains 10% water.  [#permalink]

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New post 27 Sep 2014, 00:40
munia123 wrote:
hey guys, i have got another problem. please help me to solve it.the problem says,

a mixture of 40 liters of milk and water contains 10% water. how much water should be added to this so that water may be 20% in the new mixture?

my answer is 4 liter but, i am not sure. please help me.




hi how would u solve this using the allegation method ?
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Re: A mixture of 40 liters of milk and water contains 10% water.  [#permalink]

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New post 29 Sep 2014, 01:18
1
Initial water = 4

Initial Solution = 40

Say Quantity "x" water added

Final water = 4+x

Final Solution = 40+x

\(\frac{4+x}{40+x} = \frac{20}{100} = \frac{1}{5}\)

x = 5

Answer = 5 (No OA for this question)
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Re: A mixture of 40 liters of milk and water contains 10% water.  [#permalink]

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New post 16 Apr 2017, 13:43
munia123 wrote:
hey guys, i have got another problem. please help me to solve it.the problem says,

a mixture of 40 liters of milk and water contains 10% water. how much water should be added to this so that water may be 20% in the new mixture?

my answer is 4 liter but, i am not sure. please help me.


let w=water to be added
.10*40+w=.20(40+w)
w=5 liters
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Re: A mixture of 40 liters of milk and water contains 10% water.  [#permalink]

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Re: A mixture of 40 liters of milk and water contains 10% water.   [#permalink] 07 Aug 2019, 02:59
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