Question

Arata ca: 2015|(1+2+3+...+2014) Helppp!!!

Answer 1

2015x(1+2+3...2014)=
2014x2015:2=2029105
2029105x2015=4088646575

Answer 2

$2015\cdot(1+2+3+\,...\,+2014)=2015\,\cdot\,\frac{2014\cdot2015}{2}=\\=2015^2\,\cdot\,1007=4 088 646 575$