Which of the following measurements of length is the most precise? Why?
$(i) \ 2.0 \ cm$
$(ii) \ 2.00 \ cm$
$(iii) \ 2.000 \ cm$

From the point of view of significant figures,which of the following is/are correct?
$(i)\ 11.3 \ cm + 4 \ cm = 15.3 \ cm$
$(ii)\ 4.53 \ m - 1.2 \ m = 3.3 \ m$
$(iii)\ 5.45 \ kg - 3.2 \ kg = 2.25 \ kg$
$(iv)\ 84.8 \ cm + 48.6 \ cm = 133 \ cm$

Write the rules for rounding off numbers.

Find the area of a rectangle with dimensions $1.23 \ cm$ and $2.345 \ cm$ in $cm^2$.

In an experiment on a simple pendulum to determine the acceleration due to gravity,a student measures the length of the thread as $63.2 \,cm$ and the diameter of the pendulum bob as $2.256 \,cm$. The student should take the length of the pendulum to be ........... $cm$.

The number of significant figures in the measurement of a length $0.079000 \ m$ is