Combinations

To solve this problem, we need to determine the value of such that the sum of the first natural numbers is 45.

1. Formula for Sum of First Natural Numbers:
The formula is:

2. Substituting the Given Sum:
We are given , so:

3. Multiply Both Sides by 2:

4. Solving the Equation:
We try values of to satisfy the equation:
Try : ✅

Final Answer:
The correct option is (A) 9.