How much quantity (in kg) of wheat costing Rs 84 per kg must be mixed with 81 kg of wheat costing Rs 60 per kg so that on selling the mixture at Rs 75.9 per kg, there is a gain of 15%?

Let $$x$$ kg of Rs. 84/kg of wheat is mixed with 81 kg of wheat costing Rs. 60 /kg

Selling price after 15% profit = Rs. 75.9

=> Cost price of the mixture = $$\frac{75.9}{(100+15)}\times100$$

= $$\frac{7590}{115}=Rs.$$ $$66$$

According to ques,

=> $$84(x)+60(81)=66(x+81)$$

=> $$84x+4860=66x+5346$$

=> $$84x-66x=5346-4860$$

=> $$18x=486$$

=> $$x=\frac{486}{18}=27$$

$$\therefore$$ 27 kg of wheat is required.

=> Ans - (A)