A milkman purchases the milk at Rs. x per litre and sells it at Rs. 2x per litre still he mixes 2 litres water with every 6 litres of pure milk. What is the profit percentage?

Let the cost price of 1-liter pure milk be Re.1, then 

  $6 liters \left(milk\right) \to C.P = Rs. 62 liters \left(water\right) \to C.P = Rs. 0\to CP = Rs.6 only$

8 litre mixture  =>

SP =>  8 x 2 = Rs. 16

Profit % =  $\frac{16 - 6}{6}x100 = \frac{1000}{6} = 166.66\%$