(1) S < 20 implies there can be many sums less than 20, like 1 + 2 = 3, 1 + 2 + 3 = 6 and so on.sud21 wrote:
No definite answer; NOT sufficient.
(2) S² > 220 again implies there can be many values such that S² > 220. (S² > 196 or S² > 14² or S > 14)
No definite answer; NOT sufficient.
Combining (1) and (2), 14 < S < 20
Now 1 + 2 + 3 + 4 + 5 = 15 and 1 + 2 + 3 + 4 + 5 + 6 = 21, which is not possible as it is > 20
So, there is only one possibility, that is S = 15, here n = 5; SUFFICIENT.
The correct answer is C.
