Question

Adună treimile tuturor numerelor naturale mai mici ca 16.    ??? 

Answer 1

$\frac{1}{3} + \frac{2}{3} + \frac{3}{3} + \frac{4}{3} + \frac{5}{3} + \frac{6}{3} + \frac{7}{3} + \frac{8}{3} + \frac{9}{3} + \frac{10}{3} + \frac{11}{3} + \frac{12}{3} + \frac{14}{3} + \frac{15}{3} = [tex] \frac{1+2+3+4+5+6+7+8+9+10+11+12+13+14+15}{3}$ =
$\frac{15 x16:2}{3} = \frac{240}{3} =80$

Answer 2

3:3+6:3+9:3+12:3+15:3=1+2+3+4+5=15