Răspuns:
Fie sirul de numere 1, 3, 5, 7, ...
a) 1, 3, 5, 7, 9, 11, 13, 15...
b) 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79.
Raspuns: 79.
c) 1 + 3 +5 + 7 + 9 + 11 + 13 + 15 + 17 + 19 + 21 + 23 + 25 + 27 + 29 + 31 + 33 + 35 + 37 + 39 + 41 + 43 + 45 + 47 + 49 + 51 + 53 + 55 + 57 + 59 = 100 + 125 + 175 + 225 + 275 = 225 + 400 + 275 = 625 + 275 = 900
Raspuns: 900.