Interior painting area – Exclude doors and windows:\nRoom dimensions are 10 m × 7 m × 5 m (L × B × H). Two doors of 1 m × 3 m each, one window 2 m × 1.5 m, and two windows 1 m × 1.5 m each. Find the cost to paint the walls at Rs 3 per sq m.

Introduction / Context:
Interior wall painting area equals the total area of the four walls minus the area of openings (doors/windows). Then multiply by cost per square metre.

Given Data / Assumptions:

• L = 10 m, B = 7 m, H = 5 m.
• Doors: 2 × (1 × 3) = 6 sq m.
• Windows: 1 × (2 × 1.5) = 3 sq m and 2 × (1 × 1.5) = 3 sq m ⇒ total windows = 6 sq m.
• Cost = Rs 3 per sq m.

Concept / Approach:
Wall area = perimeter * height. Paintable area = wall area − openings.

Step-by-Step Solution:

Verification / Alternative check:
Re-add doors/windows to ensure no omission: two doors (6), three windows (6) total 12 sq m ✔️

Why Other Options Are Wrong:
174, 274, 374 result from subtracting wrong openings or using L + B instead of 2(L + B).

Common Pitfalls:
Accidentally including ceiling/floor; missing one window; not converting m to sq m properly.

Final Answer:
Rs.474