1. S = 1 + 2 + 3 + .... + 100 = (100*101)/2 = 5050
2. S = 2 + 4 + 6 + .... 100 = 2 (1 + 2 + 3 + ... + 50) = 2 * (50*51)/2 = 2550
3. S = 3 + 6 + 9 + ... 702 = 3 (1+2 +3+ ... 234) = 3 * (234*235)/2 = 82485
4. S = 5 + 10 + 15 + ... + 2015 = 5 (1 +2 + 3 + ... 403) = 5* (403*404)/2 = 407030
5. S = 4 + 8 + 12 + ... 2016 = 4 (1+2+3... + 504) = 4*(504*505)/2 = 509040
formula generala este
S = 1+2+3...+n = n(n+1) /2
