Which rule should be followed when adding numbers in scientific notation?

When a decimal point is moved to the right for a very small number, the exponent of 10 becomes:

The least count of a measuring instrument means:

When a decimal point is moved to the left in scientific notation, the exponent of 10 is:

Which practice helps reduce parallax error while using a metre rule?

Which number is correctly written in scientific notation?

Why should the zero mark of a metre rule coincide with one edge of the object?

In scientific notation, the numerical part is usually written as:

Vernier calipers are mainly used to measure:

Which value is equal to 2 ms?

The least count of the Vernier calipers described in the chapter is: