In an experiment, a set of reading are obtained as follows - 1.24 mm, 1.25 mm, 1.23 mm, 1.21 mm. The expected least count of the instrwnent used in recording these readings is ___ mm.

Readings obtained: 1.24 mm, 1.25 mm, 1.23 mm, 1.21 mm. Find the expected least count of the instrument.

All readings are given to the second decimal place (hundredths of a mm), i.e., 1.21, 1.23, 1.24, 1.25 mm.

The least count of a measuring instrument is the smallest division it can measure. Since the readings vary in the hundredths place (0.01 mm), the instrument can measure up to 0.01 mm precision.

The differences between consecutive readings are multiples of 0.01 mm, confirming the least count is 0.01 mm.

The correct answer is Option 1: 0.01 mm.