A business man buys two qualities A and B of a product at Rs. 120 per kg and Rs. 60 per kg respectively. He then mixes these two qualities and sells at Rs. 100 per kg. Then the percentage increase in the profit on a certain quantity of the mixture of A and B in the ratio 7:11 on the profit on the same quantity of the mixture of A and B in the ratio 1:1, is

Business man buys two qualities A and B of a product at Rs. 120 per kg and Rs. 60 per kg respectively.

Let say, When he mixes A and B in 1:1, he produces 2kg of 180 Rs. product.

So, 1kg of mixture cost price 90 Rs.

He sold it at 100 Rs/kg.

So,Profit=100-90=10 Rs/kg.

Again ,

Let say, When he mixes A and B in 7:11, he produces 18 kg of (840+660)=1500 Rs. product.

So, 1 kg of mixture cost price $$\frac{1500}{18}$$ Rs.

So, profit=$$100-\frac{1500}{18}=\frac{300}{18}=\frac{50}{3}$$ Rs/kg.

So, percentage increase in profit=$$\frac{\left(\frac{50}{3}-10\right)}{10}\times100=\frac{20}{30}\times100=\frac{200}{3}.$$

D is correct choice.