Question

Calculati suma tuturor numerelor naturale de trei cifre care împărţite la 31 dau restul 13.

Answer 1

x:31=c rest 13 x=31c+13 x-13=31c+13-13 x-13=31c x-13∈M31 M31={31,62,93,124,155,186,217,248,279....} x-13=93 x=93+13 x=106 106:31=3 rest 13 e bun x-13=124⇒x=137 137:31=4 rest 13 x-13=155⇒x=168 168:31=5 rest13 x-13=186⇒x=199 199:31=6 rest 13 nr.sunt:106,137,168,199.......