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

Question

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

Bunuel · Accepted Answer

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.

schebro · Answer

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.

vitamingmat · Answer

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???

Bunuel · Answer

4+x liters of water is 20% of 40+x liters of mixture not 40.

munia123 · Answer

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 .

TGC · Answer

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

sugand · Answer

hi how would u solve this using the allegation method ?

PareshGmat · Answer

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)

gracie · Answer

let w=water to be added
.10*40+w=.20(40+w)
w=5 liters

fireagablast · Answer

Given 40L water/milk, with water = 10%
40*0.1 = 4

(40+x)*20% = 4+x
(40+x)/5 = 4+x
40+x = 20+5x
20=4x
x=5 ---> need to add 5L of water

Check
40+5= 45
45/5=9 --20%
4+5=9---good

akshita23 · Answer

10% water in 40lit
90% milk in 40lit
we need to mix 100% pure water to get 20% water content in mixture
100% 10%
 20%
w1/w2=20-10/100-20
w1/40=10/80
w1=5lit of water needs to be added

bumpbot · Answer

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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.

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