Differentiate between the determination of density of regular solids and determination of density of irregular solids?

The density of regular solid:

1. Use a ruler to measure the length (l), width (w) and height (h) of the object.
2. Place the object on the top pan balance and measure its mass.
3. Calculate the volume of the cube using $l\times w\times h$ .
4. Use the measurements to calculate the density of the object with $\rho =\frac{m}{V}$, where m is mass and V is volume.

The density of irregular solid:

1. Place the object on the top pan balance and measure its mass.
2. Fill a measuring cylinder so that there is enough water to cover the object when it is placed inside the cylinder. Take the reading of the volume.
3. Carefully lower the object into the cylinder.
4. Take the new reading of the volume. Subtract the original reading to obtain the volume of the object.
5. Use the measurements to calculate the density of the stone $\rho =\frac{m}{V}$, where m is mass and V is volume.