The number of significant figures in $0.00051$ is:

The dimensions of an aluminum block are $3.0 \, \text{inch} \times 4.0 \, \text{inch} \times 5.0 \, \text{inch}$. What is the mass of this block in grams? The density of aluminum is $2.7 \, \text{g/cm}^3$ and $1 \, \text{inch} = 2.54 \, \text{cm}$.

What is the temperature of $343 \ K$ in $^\circ F$ (in $^\circ F$)?

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 ....

$25^{\circ} C$ temperature in Fahrenheit and Kelvin scales are respectively:

What is the $SI$ unit of mass? How is it defined?