Profit percentage = 166 2/3% (i.e. 166.66%).

Step-by-step explanation

Let the cost price of pure milk be xxx rupees per litre.

  • He buys 6 litres of pure milk.

    • Cost price of 6 litres of milk
      =6x=6x=6x rupees.

  • He mixes 2 litres of water with these 6 litres.

    • Water is assumed to be free , so its cost is 000.

So, total quantity of mixture
=6+2=8=6+2=8=6+2=8 litres. He sells the mixture at Rs. 2x2x2x per litre.

  • Selling price of 8 litres
    =8×2x=16x=8\times 2x=16x=8×2x=16x rupees.

Now compute profit:

  • Profit
    =SP−CP=16x−6x=10x=\text{SP}-\text{CP}=16x-6x=10x=SP−CP=16x−6x=10x.

  • Profit percentage

Profit %=ProfitCP×100=10x6x×100=106×100=53×100=16623%.\text{Profit %}=\frac{\text{Profit}}{\text{CP}}\times 100 =\frac{10x}{6x}\times 100 =\frac{10}{6}\times 100 =\frac{5}{3}\times 100 =166\frac{2}{3}%.Profit %=CPProfit​×100=6x10x​×100=610​×100=35​×100=16632​%.

Final answer

The milkman’s profit percentage is

16623% (i.e. 166.66%)\boxed{166\frac{2}{3}%\text{ (i.e. }166.66%\text{)}}16632​% (i.e. 166.66%)​