A student measured the length of a rod and

Question:
A student measured the length of a rod and wrote it as $3.50 \mathrm{~cm}$. Which instrument did he use to measure it ?

A screw gauge having 100 divisions in the circular scale and pitch as $1 \mathrm{~mm}$.
A screw gauge having 50 divisions in the circular scale and pitch as $1 \mathrm{~mm}$
A meter scale
A vernier calliper where the 10 divisions in vernier scale matches with 9 division in main scale and main scale has 10 divisions in $1 \mathrm{~cm}$.

Correct Option: , 4

Solution:

Least count of varnier calliper is $0.01 \mathrm{~cm}$ Hence it matches with the reading.