A metre stick is balanced on a knife edge at its centre. When two coins, each of mass 6 g put one on top of the other at the 12.0 cm mark, the stick is found to be balanced at 45.0 cm. What is the mass of the metre stick?

Explanation

To solve the problem, we need to analyze the situation using the principle of moments (torque) around the pivot point (knife edge).

### Step-by-Step Solution:

1. **Identify the Given Data:**
- Mass of one coin, \( m = 6 \, \text{g} \)
- Total mass of two coins, \( M_c = 2 \times m = 2 \times 6 \, \text{g} = 12 \, \text{g} \)
- Initial balance point of the meter stick is at its center (50 cm mark).
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