The prefix zepto stands for

Fill in the blanks given below:
$(i)$ At ........ ${\,^\circ }{\text{C}}$,the values of temperature in both ${\,^\circ }{\text{C}}$ and ${\,^\circ }{\text{F}}$ are equal.
$(ii)$ The number of significant figures in $0.03$ is .....
$(iii)$ The closeness of various measurements for the same quantity is called .........
$(iv)$ The agreement of a particular value to the true value of the result is called ....

If the number of $H^{+}$ ions in $1 \ L$ of distilled water is $6.023 \times 10^{16}$,what is the number of $H^{+}$ ions in $1 \ mL$ of distilled water?

Define significant figures.

In the final answer of the expression $\frac{(29.2 - 20.2)(1.79 \times 10^5)}{1.37}$,the number of significant figures is

What do you mean by significant figures?