Question

Aratati ca nr 1+2+3+....+1994+1995 se împarte exact la 1995

Answer 1

$1 + 2 + 3 + ... + 1994 + 1995$

$= \frac{1994(1994 + 1)}{2} + 1995$

$= \frac{1994 \times 1995}{2} + 1995$

$= 997 \times 1995 + 1995$

$= 1995(997 + 1) = 1995 \times 998 \: \: \vdots \: \: 1995$