Explanation:

- When a mobile phone is sold at a profit of 80%, the selling price is 180% of the cost price.

- To find the profit as a percentage of the selling price, use the formula: $$\text{Profit percentage of selling price} = \left(\frac{\text{Profit}}{\text{Selling Price}}\right) \times 100\%$$

- Let the cost price be \(100\) units. The profit is then \(80\) units (since 80% of 100).

- The selling price is \(180\) units (100 units cost price + 80 units profit).

- Plugging these values into the formula: $$\left(\frac{80}{180}\right) \times 100\% = 44.44\%$$

- Correct Answer: Option 3: 44.44%