Question

The smallest division on the main scale of a Vernier callipers is $1\text{mm}$ and 10 vernier divisions coincide with 9 main scale divisions. While measuring the diameter of a ring, the zero mark of the vernier scale lies between $5.0\text{cm}$ and $5.1\text{cm}$ and the eighth division of the vernier scale coincides with a main scale division. The diameter of the ring is :

Answer 1

$10VSD=9MSD$
$1VSD=0.9MSD$
$1VSD=0.9\times 1\text{mm}=0.9\text{mm}$
Least count = $1MSD-1VSD=0.1\text{mm}$

Reading = main scale reading + vernier scale reading $=5.0+8\times 0.01=5.08\text{cm}$.