alligation or mixture aptitude questions
2.  Tea worth Rs. 126 per kg and Rs. 135 per kg are mixed with a third variety in the ratio 1 : 1 : 2. If the mixture is worth Rs. 153 per kg, the price of the third variety per kg will be:  
Answer: Option C Explanation:
Since first and second varieties are mixed in equal proportions.
So, the mixture is formed by mixing two varieties, one at Rs. 130.50 per kg and the other at say, Rs. x per kg in the ratio 2 : 2, i.e., 1 : 1. We have to find x. By the rule of alligation, we have:
x – 153 = 22.50 x = 175.50 
3.  A can contains a mixture of two liquids A and B is the ratio 7 : 5. When 9 litres of mixture are drawn off and the can is filled with B, the ratio of A and B becomes 7 : 9. How many litres of liquid A was contained by the can initially?  
Answer: Option C Explanation:
Suppose the can initially contains 7x and 5x of mixtures A and B respectively.
252x – 189 = 140x + 147 112x = 336 x = 3. So, the can contained 21 litres of A. 
4.  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 containers so as to get 12 litres of milk such that the ratio of water to milk is 3 : 5?  
Answer: Option B Explanation:
Let the cost of 1 litre milk be Re. 1
By the rule of alligation, we have:

5.  In what ratio must a grocer mix two varieties of pulses costing Rs. 15 and Rs. 20 per kg respectively so as to get a mixture worth Rs. 16.50 kg?  
Answer: Option C Explanation:
By the rule of alligation:
Required rate = 3.50 : 1.50 = 7 : 3. 