Least count is defined as the ratio of minimum reading on main scale and the number of division on vernier scale

It is given as minimum reading of main scale = 1 mm

total number of divisions = 10

so least count of the scale is 0.01 mm

Pitch = Main scale reading revealed on rotating circular disc / No of rotations

= 5mm/10 rotations

=0.05mm

Hope this helps... Thank you.

Least count = pitch / no of division on circular scale

=0.5mm/50

=0.001mm

Thanks