Question

3+6+9+....+180 cum se calculeaza

Answer 1

3+6+9+....+180= 3(1+2+3+...+60)
Pentru paranteza folosim formula Gauss:
1+2+3...+n=n(n+1)/2,
1+2+3+..+60=60x61/2=1830⇒

3+6+9+...+180=3(1+2+3+...+60)=3x1830=5490

Answer 2

3 + 6 + 9 + ......+180 = 
n = ( 180 - 3) : ( 6 - 3 ) +1 
n = 177 : 3 + 1
n = 59 + 1
n = 60
S = [( 180 + 3) x 60 ] : 2
S = ( 183 x 60 ) : 2 
S = 10980 :2 
S = 5490.