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### Question

In what ratio should a vendor mix two types of pulses costing Rs. 16/Kg and Rs. 21/Kg respectively so as to get a mixture of Rs. 18/Kg?

**A**

$1{1/2}$.

**B**

$2{1/2}$.

**C**

$3{1/2}$.

**D**

$2{1/4}$.

**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} = 21, A_{1} = 16, A = 18 we have n_{1} × (18 - 16) = n_{2} × (21 - 18), from where we get the required ratio as $n_1/n_2 = 3 : 2$.