A merchant mixes three varieties of rice costing Rs.20/kg, Rs.24/kg and Rs.30/kg and sells the mixture at a profit of 20% at Rs.30 / kg. How many kgs of the second variety will be in the mixture if 2 kgs of the third variety is there in the mixture? Choose one:  A) 1 kgs  B) 3 kgs  C) 5 kgs  D) 6 kgs  E) None of these
Explanation :   If the selling price of mixture is Rs.30/kg and the merchant makes a profit of 20%, then the cost price of the mixture = 30/1.2 = Rs.25/kg.   We need to find out the ratio in which the three varieties are mixed to obtain a mixture costing Rs.25 /kg.   Let variety A cost Rs.20/kg, variety B cost Rs.24 / kg and variety C cost Rs.30/kg. The mean desired price falls between B and C.   Step 1:   Find out the ratio Qa:Qc using alligation rule.   Qa/Qc=(30−25)/(25−20)=1/1.   Step 2:   Find out the ratio Qb:Qc using alligation rule.   Qb/Qc=30−25/(25−24)=5/1.   Step 3:   Qc is found by adding the value of Qc in step 1 and step 2 =1+1= 
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2.   Therefore, the required ratio=1:5:2.   If there are 2 kgs of the third variety in the mixture, then there will be 5 kgs of the second variety in the mixture.   Answer : 5 kgs
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A merchant mixes three varieties of rice costing Rs.20/kg, Rs.24/kg and Rs.30/kg and sells the mixture at a profit of 20% at Rs.30 / kg. How many kgs of the second variety will be in the mixture if 2 kgs of the third variety is there in the mixture?