A right circular cone has curved surface area (lateral area) 99 cm² and slant height 9 cm.\nFind its diameter in centimetres.

Introduction / Context:
The curved surface area (CSA) of a right circular cone is CSA = π * r * l, where r is the base radius and l is the slant height. Given CSA and l, we can recover r and then the diameter 2r.

Given Data / Assumptions:

• CSA = 99 cm²
• Slant height l = 9 cm

Concept / Approach:
Compute r = CSA / (π * l). Using π = 22/7 yields an exact value here. Then diameter D = 2r.

Step-by-Step Solution:

Verification / Alternative check:
CSA back-check: π * r * l = (22/7) * 3.5 * 9 = (22/7) * 31.5 = 99 cm², consistent.

Why Other Options Are Wrong:
3.5 is the radius (not diameter); 10.5 and 14 assume incorrect r; 7 is the correct diameter.

Final Answer:
7