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### Question

12 liters of Petrol costing Rs. 5/liter is mixed with 6 liters of Kerosene costing Rs. 14/liter. What is the price of the mixture per liter?

**A**

Rs. 8 per liter.

**B**

Rs. 9 per liter.

**C**

Rs. 7 per liter.

**D**

Rs. 11 per liter.

**Soln.**

**Ans: a**

We shall use the alligation formula. If a sample n_{1} has an average price of A_{1}, and another sample n_{2} has an average price of A_{2}, then the price of the mixture, A, is determined by the alligation formula as: n_{1}(A - A_{1}) = n_{2}(A_{2} - A). Putting A_{2} = 14, A_{1} = 5, n1 = 12, n2 = 6, we have 12 × (A - 5) = 6 × (14 - A), from where we get A = Rs. 8 per liter.