Alligations or Mixtures
Aptitude

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Q.

A milk vendor has 2 cans of milk .The first contains 25% water and the rest milk. The second contains 50% water.

How much milk should he mix from each of the container so as to get 12 litres of milk such that the ratio of water to milk is 3:5?

 A.

6 litres

 B.

1 litres

 C.

8 litres

 D.

7 litres

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Solution:
Option(A) is correct

Milk in 1 litre mixture in 1st can = 3/4 litre. 
Milk in 1 litre mixture in 2n d can = 1/2 litre. 
Milk in 1 litre final mixture = 5/8 litre. 
By rule of alligation we have required ratio 5 : 8

3/4                        1/2

 

         \                 /
               (5/8)

         /                 \

 

1/8              :            1/8    

Therefore ratio of two mixtures: 
$=\dfrac{1}{8}:\dfrac{1}{8}$
$=1:1$

So, quantity of mixture taken from each can,
$=\dfrac{1}{2}\times 12$
$= 6$ litres


(2) Comment(s)


Harshal
 ()

1st can can not contain 75% water. Ratio of milk to total mixture must be greater than $\dfrac{5}{8}$ since other can already contains lesser ration of milk ($\dfrac{1}{2}$).

Two can of less milk can not give higher milk percentage when mixed.



Anonymous
 ()

Question is wrong!

The first can should contain $25\%$ water and rest milk.