misal :

Diket :

a = 2r

π = 3,14

Volume kubus = a3 = (2r)3 = 8r³

Volume atom = (8 × 1/8 )4/3 πr³

= 4/3 πr³

P.E = Volume atom : volume kubus

= 4/3 πr³ : 8r³

= π : 6

= 3,14 : 6

= 0, 52

= 0,52 × 100 %

= 52%