Alligations or Mixtures
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Q.

How many litres of a 12 litre mixture containing milk and water in the ratio of 2 : 3 be replaced with pure milk so that the resultant mixture contains milk and water in equal proportion?

 A.

1.0 litres

 B.

1.5 litres

 C.

2.0 litres

 D.

4.0 litres

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Solution:
Option(C) is correct

The mixture contains 40% milk and 60% water in it. That is 4.8 litres of milk and 7.2 litres of water.

Now we are replacing the mixture with pure milk so that the amount of milk and water in the mixture is 50% and 50%.That is we will end up with 6 litres of milk and 6 litres of water.

Water gets reduced by 1.2 litres.

To remove 1.2 litres of water from the original mixture containing 60% water, we need to remove $\dfrac{1.2}{0.6}$ litres of the mixture = 2 litres.

Note: Thank you Deepankar and Rajashekar  for pointing out the correction in the comments, final answer has been changed to 2.0 litres from 1.5 litres.


(9) Comment(s)


Kalyan Venkatesh
 ()

1/2=3/5(1-x/12)

x=12/2

x=6


Vivek Bodh
 ()

Hello kalyan could you please elaborate on this. As there is a confusion regarding the usage of 1 - X/12.


Nimesh Goyal
 ()

1/2 = 3/5 (1- x/1)^1

x= 1/6

ie. the ratio of liquid replaced per litre.

answer = 1/6 X 12 = 2 liters

[ THIS IS THE SAME METHOD AS USED IN QUESTION NO. 1 AND SOME OTHER PREVIOUS QUESTIONS ]



Prajyoti
 ()

I dint understand last line. Can u explain this??



Rajashekar
 ()

answer is 2 litres...but this is marked for 1.5 litres as correct.


Deepak
 ()

Thank you for pointing out. Changed the answer to suit the need.


Deepankar
 ()

Answer should be Option (c) i.e. 2 litres..


Amit Bhandari
 ()

exactly!!!!!!!!!!!!!!!!!!!!!!!!!!1

Deepak
 ()

Thank you for pointing out the aberration. Changed the answer choice.