Răspuns:
Explicație pas cu pas:
abc
cazuri fav 1b1, 2b2, ...2 cazuri
cazuri posibile 2*2*2=...2³....8 cazuri
P=2/8=1/4=25%
[tex]\displaystyle\bf\\\textbf{Numerele de 3 cifre formate cu cifrele 1 si 2 sunt:}\\\\111\\112\\121\\122\\211\\212\\221\\222\\In~total~sunt~8~numere=\boxed{\bf8~cazuri~posibile}.\\\\Dintre~acestea,~numerele~cu~prima~si~ultima~cifra~egale~sunt\!\!:\\\\111\\121\\212\\222\\In~total~sunt~4~numere=\boxed{\bf4~cazuri~favorabile}.\\\\p=\frac{Numar~cazuri~favorabile}{Numar~cazuri~posibile}=\frac{4}{8}=\frac{1}{2}= 0,5=50\%\\\\\boxed{\bf p=50\%}[/tex]
