While measuring the length of a rod with a vernier callipers, figure below shows the position of its scales. What is the length of the rod?

As we know,

$\text{Least count (L.C.)} = \dfrac{\text{ Value of 1 main scale div (x)}}{\text{total no. of div on vernier (n)}}$

There are 10 divisions on 1 cm on the main scale

Therefore,

$\text{Value of 1 main scale division(x)} = \dfrac{1}{10}\text{ cm} = 0.1 \text{cm} \\[0.5em]$

Total number of divisions on the vernier scale (n) = 10

$\text{Least count (L.C.)} = \dfrac{0.1}{10} \\[0.5em] \text{L.C.} = 0.01 \text {cm}\\[0.5em]$

Hence, the least count = 0.01 cm.

Given,

Main scale reading = 3.3 cm

coinciding division = 6

As we know,

$\text{Vernier scale reading} = \text{Vernier scale division} \times \text{L.C.} \\[0.5em] \text{Vernier scale reading} = 6 \times 0.01 \text{cm} \\[0.5em] \Rightarrow \text{Vernier scale reading} = 0.06 \text{cm} \\[0.5em]$

Hence, Vernier scale reading is 0.06 cm.

$\text{Observed reading} = \text{main scale reading} + \text{vernier scale reading} \\[0.5em] \text{Observed reading} = 3.3 \text{cm} + 0.06 \text{cm} \\[0.5em] \Rightarrow \text{Observed reading} = 3.36\text{cm} \\[0.5em]$

Hence, the length of the rod is 3.36 cm.