A vernier callipers has its main scale graduated in mm and 10 divisions on its vernier scale are equal in length to 9 mm. When the two jaws are in contact, the zero of vernier scale is ahead of zero of main scale and 3rd division of vernier scale coincides with a main scale division. Find the zero error of vernier callipers.

Explanation

To find the zero error of the vernier calipers, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Main Scale Division (MSD)**:
- The main scale is graduated in mm. Therefore, 1 MSD = 1 mm.

2. **Determine the Length of the Vernier Scale**:
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