A vernier has 10 divisions and they are equal to 9 divisions of main scale in length. If the main scale is calibrated in mm, what is its least count?

Explanation

To find the least count of the vernier scale, we will follow these steps:

### Step 1: Understand the relationship between the Vernier scale and the main scale.
We know from the problem statement that 10 divisions of the Vernier scale are equal to 9 divisions of the main scale in length.

### Step 2: Calculate the length of one Vernier scale division.
Since 10 Vernier scale divisions are equal to 9 main scale divisions, we can express the length of one Vernier scale division (VSD) in terms of the main scale division (MSD).

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