JEE Main · 2026 · 28 Jan 2026 · Shift 2 · Units & Measurement

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

(A)0.01✓ Correct
(B)0.001
(C)0.1
(D)0.05

Answer: (A)

Solution

The least count of an instrument is the smallest change it can resolve, and it is reflected in the last place to which readings are expressed. The four readings

1.24

mm,

1.25

mm,

1.23

mm and

1.21

mm are all quoted to the second decimal place, i.e. to the nearest hundredth of a millimetre. Hence the least count of the instrument is

0.01

mm.

JEE Main · 2026 · 28 Jan 2026 · Shift 2 · Single correct option

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