A room 5 m $\times$ 8 m is to be carpeted leaving a margin of 10 cm from each wall. If the cost of the carpet is ₹ 18 per Sq. metre, the cost of carpeting the room will be

### Concept & Area Cost Calculation Adjust total dimensions by subtracting boundary margins, ensuring all units are uniform before calculating the total cost. $$ Total Cost = Area \times Cost Per Unit $$ ### Step-by-Step Solution * Room dimensions and margin requirements are validated and normalized to meters. * Standard subtraction yields the effective spatial dimensions. * Final arithmetic operation directly computes the definitive cost of ₹ 673.92. ### Exam Strategy & Shortcut Calculate carpet dimensions as $4.8$ and $7.8$. Focus purely on the last digits: $8 \times 8 = 64$ (ends in 4). Cost ends in 8. $4 \times 8 = 32$. The final answer must end in `.92`. Option A is the only match. ### Common Pitfall Failing to convert the 10 cm margin into standard meters (0.1 m) prior to deducting it from the principal room dimensions. ### Final Answer Therefore, the correct answer is **₹ 673.92**.