1. Numerele trebuie sa aiba 5 cifre.Rezulta ca vor fi de forma: abcde
a apartine {1,2,3,4,5,6,7,8,9}
b apartine {0,1,2,3,4,5,6,7,8,9}
c apartine {0,1,2,3,4,5,6,7,8,9}
d apartine {0,1,2,3,4,5,6,7,8,9}
e apartine {0,1,2,3,4,5,6,7,8,9}
b,c,d,e au 10 cazuri sia doar 9 ⇒Nr. de umere posibile 9×10×10×10×10=9×10000=90000