1 to 100 sum Brain teaser

What is the sum of numbers from 1 to 100?

 Answer 1: The trick here is that you have 50 pairs which each sum to 101 (e.g. 1+100, 2+99, 3+98, etc.). So, 50 times 101 = 5050.

 Answer 2: using formula
sum = n(n+1)/2
        = 100(100+1)/2
        = 50(101)
        = 5050

Answer 3: Now we are presenting interesting trick for you:
1 to 100 sum = 1 + 2 + 100 = 103