Solution :
The atomic mass of aluminium is given to be 27 u.
So, 1 mole of aluminium atoms has a mass of 27 grams.
Now, 1 mole of aluminium atoms = 27 g.
So,
4 moles of aluminium atoms = 27 x 4 g
= 108 g
Thus, The mass of 4 moles of aluminium atoms is 108 grams.