A stockiest wants to make some profit by selling sugar. He contemplates about various methods. Which of following would maximize his profit?
I. Sell sugar at 10% profit.
II. Use 900 g of weight instead of 1 kg.
III. Mix 10% impurities in sugar and selling sugar at cost price.
IV. Increase price by 5% and reduced weights by 5%.

Let the CP of 1 kg of sugar be Rs. 100.
Then, CP of 900g sugar = $$\frac{{100 \times 900}}{{1000}}$$   = Rs. 90
Hence, profit % = $$ {\frac{{100 - 90}}{{90}}} \times 100$$     = 11.11%

If he add 10% impurity then his CP for 1 kg = $$\frac{{100 \times 1000}}{{1100}}$$   = Rs. 90.9
And % profit = $$ {\frac{{100 - 90.9}}{{90.9}}} \times 100$$     = 10.01%

If he reduces weight by 5% Then, cost price of 950 g = $$\frac{{100 \times 950}}{{1000}}$$   = Rs 95 and SP = 105;
% profit = $$ {\frac{{105 - 95}}{{95}}} \times 100$$     = 10.25%