Question

Calculati suma anilor bisecti de la 1600 pana la 1918

Answer 1

cum 2016 este an bisect  => 2016-400 =1616 an bisect => 1600 an bisect
deci suma anilor bisecti este suma numerelor (din 4 in 4 de la 1600 pana la 1918)
cum 1918 =1600 +316   ,316 divizibil cu 4 => 1918 an bisect =>
S=1600+1604+1608+...+1918 =>
=> S=(1600+0*4) +(1600+1*4 ) +(1600+2*4) +...+(1600+79*4)=>
=> S=1600*80 + (1*4+2*4+...+79*4)=>
=>S=1600*80 + 4*(1+2+3+...+79)=>
=> S=1600*80+4*(1+79)*79/2 =>
=>S=1600*80+2*80*79=>
=>S=80*(1600+158) =80*1758