Explanation:

- Let's assume the cost price is \( C \) and the original selling price is \( S \).

- Original profit is \( S - C \).

- If the selling price doubles, it becomes \( 2S \).

- New profit will be \( 2S - C \), which is given to be triple the original profit.

- Therefore, \( 2S - C = 3(S - C) \).

- Simplifying gives \( 2S - C = 3S - 3C \).

- Rearrange to get \( S = 2C \).

- Hence, the profit percentage is \(\frac{S-C}{C} \times 100\).

- Substituting \( S = 2C \) results in \(\frac{C}{C} \times 100 = 100\% \).

Option:3, 100 is correct.