The long scale which you see on the vernier calliper is the main scale
it gives you the main reading but for the accurate value we also use the small vernier scale built on the movable arm.first you put cylinder in the jaws of vernier calliper .you have to take reading from the main scale and then you have to choose the best coinciding line(main scale wihh vernier scale) and multiplying that line no. with vernier constant which is 0.01 and then adding this value to the main scale reading you get your accurate reading.
Here are the options...
1)The value of one MSD divided by total number of divisions in the main scale
2)The value of one VSD divided by total number of divisions in the vernier scale
3)The difference between the value of one main scale division and then vernier scale division
4)The difference between the value of one main scale division and one vernier scale division
Now what do you think is the answer?
d)The difference between the values of one main scale division and one vernier scale division is known as Vernier Constant.
A vernier constant is a constant which allows a distance or angle measurement to be read more precisely than directly reading a uniformly-divided straight or circular measurement scale using devices like vernier caliper.
you better solve your queries in school. internet is not for this purpose . i am from los angeles
is it trrue answer