def cgpa(grades: list[float]) -> float:
    """Calculate CGPA from list of grade points."""
    if not grades:
        raise ValueError("Grades list cannot be empty")
    return sum(grades) / len(grades)


def cgpa_to_percentage(cgpa_value: float) -> float:
    """Convert CGPA to percentage (common formula)."""
    return cgpa_value * 9.5
