A milkman mixes 2 litres of water for every 6 litres of milk. The cost price of 1 litre of milk is Rs. 80. He marks up the price of the milk by 20% and gives a discount of 10% to the customers. Find the net profit percentage of the milkman.(Assume the cost of water to be negligible)

Given the milkman mixes 2 litres of water for every 6 litres of milk.

As the cost of water is negligible, the cost price of 8 litres of mixture is 6*80 = Rs. 480.

And the cost price of 1 litre of mixture is $$\frac{480}{8}=60$$.

Now he marks up the cost price of milk by 20% i.e. 

So, the marked price of 1 litre of milk is $$80\times\left(1+\frac{20}{100}\right)=96$$

And he gives a discount of 10%,

So the selling price of 1 litre of milk is $$96\times\left(1-\dfrac{10}{100}\right)=86.4$$

Hence, the profit percentage is $$\frac{86.4-60}{60}=\frac{26.4}{60}=44\%$$

Hence, the answer is 44%.