The cost of 4 dozen papers is ₹ 24. The cost of 1 score of papers (in rupees) is ....... [APTET, 2011]

### Concept & Unit Conversions To solve this, you must know standard numeric quantities. $$ 1 \text{ dozen} = 12 \text{ items} $$ $$ 1 \text{ score} = 20 \text{ items} $$ ### Step-by-Step Solution * **Identify Quantities:** * $4 \text{ dozen} = 4 \times 12 = 48 \text{ papers}$. * $1 \text{ score} = 20 \text{ papers}$. * **Find Unit Price:** * Cost of 48 papers = ₹ 24. * Cost of 1 paper = $\frac{24}{48} = ₹ \frac{1}{2}$ or ₹ 0.50. * **Calculate Required Cost:** * Cost of 20 papers = $20 \times \frac{1}{2}$ * Cost = ₹ 10. ### Exam Strategy & Shortcut Use ratios directly: $\frac{\text{Cost}_1}{\text{Quantity}_1} = \frac{\text{Cost}_2}{\text{Quantity}_2}$ $\frac{24}{48} = \frac{x}{20} \implies \frac{1}{2} = \frac{x}{20} \implies x = 10$. ### Common Pitfall The most frequent mistake is not knowing what a "score" represents and guessing incorrectly, or confusing dozen (12) with a score (20). ### Final Answer Therefore, the correct answer is **10**.