Step-by-step explanation:
The given data is as follows.
 density = 2.70 g, volume = 348 ml 
It is known that density is mass divided by volume.
Mathematically, Density = 

Hence, putting the given values into the above formula and calculate the mass as follows.
 Density = 

 2.70 g/ml = 

 = 939.6 g
Therefore, mass of given piece of aluminium is 939.6 g.