How many terms of the AP `-15, -13, -11, … ` are needed to make the sum `-55` ?

Explanation

To solve the problem of finding how many terms of the arithmetic progression (AP) `-15, -13, -11, ...` are needed to make the sum `-55`, we can follow these steps:

### Step-by-Step Solution

1. **Identify the first term (A) and common difference (D)**:
- The first term \( A = -15 \).
- The common difference \( D \) can be calculated as:
\[
...