Question

2+4+6+8+.....100
3+6+9+.......30
2+4+6+8+......2000
(Suma lui Gausse)

Answer 1

2+4+6+8+.....+100=

= 2(1+2+...+50)

= 2·50·51 : 2

= 50·51

=


3+6+9+.......+30 = 

= 3(1+2+...+10)

= 3·10·11 : 2 

= 3·5·11

=


2+4+6+8+......+2000 = 

= 2(1+2+...+1000)

= 2·1000·1001 : 2

= 1000·1001

=