Question

Why and how we are taking least count as mean absolute error in problems without actually calculating it?

Answer 1

The "Least Count" of any measuring equipment is the smallest quantity that can be measured accurately using that instrument.Thus Least Count indicates the degree of accuracy of measurement that can be achieved by the measuring instrument.

The error made in an instrument can be compared with another by calculating the percentage uncertainty of each of the readings obtained. The one with the least uncertainty is always taken to measure objects, as all measurements are required with accuracy in mind.

The smaller the measurement, the larger the percentage uncertainty. The least count of an instrument is indirectly proportional to the accuracy of the instrument.