Question

calculeaza 1+2+3+.......+60b)1+2+3+.......+73c)1+2+3+.......+120d)1+2+3+.......155

Answer 1

$a)1 + 2 + 3 + ... + 60$

$= \frac{60(60 + 1)}{2} = \frac{60 \times 61}{2} = 30 \times 61 = 1830$

$b)1 + 2 + 3 + ... + 73$

$= \frac{73(73 + 1)}{2} = \frac{73 \times 74}{2} = 73 \times 37 = 2701$

$c)1 + 2 + 3 + ... + 120$

$= \frac{120(120 + 1)}{2} = \frac{120 \times 121}{2} = 60 \times 121 = 7260$

$d)1 + 2 + 3 + ... + 155$

$= \frac{155(155 + 1)}{2} = \frac{155 \times 156}{2} = 155 \times 78 = 12090$