[tex]nr. \: cazuri \: posibile = 40[/tex]
[tex]nr. \: prime \: de \: la \: 1 \: la \: 40 \: :[/tex]
[tex]2,3,5,7,11,13,17,19,23,29,31,37.[/tex]
[tex] = > nr. \: cazuri \: favorabile = 12[/tex]
[tex]P = \frac{nr. \: cazuri \: favorabile}{nr. \: cazuri \: posibile} = \frac{12}{40} = \frac{3}{10} [/tex]