Question

(1+1/2)+(2+1/2)+(3+1/2)+......+(20+1/2)

Answer 1

$1+2+3+...+20+20* \frac{1}{2}$
$=1+2+3+...+20+10$
$1+2+3+...+n = \frac{n(n+1)}{2}$
$1+2+3+...+20 = \frac{20(20+1)}{2}$
$1+2+3+...+20 = 210$
$=>210+10=220$