Explanation:

- Vishal sold his article for ?1,818, incurring a 10% loss.

- This means Vishal's cost price was higher. The formula to find the cost price when loss is involved is: \(\text{Cost Price} = \frac{\text{Selling Price}}{1 - (\text{Loss Percentage}/100)}\).

- \(\text{Vishal’s Cost Price} = \frac{1818}{0.9} = 2020\).

- Param sold his article for ?1,818, gaining a 1% profit.

- For Param, the cost price calculation with profit is: \(\text{Cost Price} = \frac{\text{Selling Price}}{1 + (\text{Profit Percentage}/100)}\).

- \(\text{Param’s Cost Price} = \frac{1818}{1.01} = 1800\).

- The ratio of Vishal’s to Param’s cost price is \(2020 : 1800\).

- Simplifying the ratio, we get \(101 : 90\).

- Correct Answer: 101 : 90