Explanation:

- Rashi is initially 15th from the left.

- Ramesh is initially 29th from the right.

- After interchanging, Rashi becomes 26th from the left.

- To find the number of children, use the formula: initial position of Ramesh from the right + new position of Rashi from the left - 1.

- So, the total number of children is 29 (Ramesh's position from the right) + 26 (Rashi's new position from the left) - 1 = 54.

- Option 3 - 54 is: the correct answer.