Răspuns :
3 + 6 + 9 + 12 + ..... + 300 =
3(1 + 2 + 3 + 4 +.......+ 100) =
3 * 100 * 101 : 2 =
3 * 101 * 50 =
15 150
3(1 + 2 + 3 + 4 +.......+ 100) =
3 * 100 * 101 : 2 =
3 * 101 * 50 =
15 150