Question

Find the sum of all nature odd no less then 100

Answer 1

1+3 = 4

1+3+5 = 9

1+3+5+7 = 16

1+3+5+7+9 = 25

From 1 to 100, there are 50 odd numbers. Their sum is 50^2. Their average is 50*50/50 = 50.

Alternatively,

1+99 = 100

3+97 = 100

5+95 = 100 and so on.

You have 25 hundreds. Their average is 2500/50 = 50.

I hope It will help you