(n+1)/2   = 50(50+1)/2 = 1275
OR

Easy way to do it is as follows Pair up the 1st number with the last number ie 1 and 50 which adds up to 51 Pair up 2nd and second from last ie 2 and 49 which adds up to 51 There are 25 such pairs from 1 to 50 so you multiply 51 times 25 to get your answer. In one step its 25 x 51 = 1275 Thanks for playing.


what is the difference?