Since your question starts with the number 1, we can decide if we want to handle that specific series (even, 100 numbers) or add the 0 to make it odd without affecting the total sum.
I’ll do both.
For the odd series:
0 + 100 = 100
1 + 99 = 100
…
48 + 52 = 100
49 + 51 = 100
The pairwise sum is 100.
The number of pairs are 50.
The sum of all pairs are 50*100 = 5000
We add the unpaired center number 5000 + 50 = 5050
For the even series:
1 + 100 = 101
2 + 99 = 101
…
49 + 52 = 101
50 + 51 = 101
The pairwise sum is 101.
The number of pairs are 50.
The sum of all pairs are 50*101 = 5050
No unpaired center number
Another Solution of What is the total number of digits from 1 to 100?
Sum of Numbers Starting from 1 in a interval of 1 is given by
Sum=N×(N+1)/2
N= Last Number i.e. 100 here
Therfore ,
Sum =100×101/2
=5050