**Question:**

What is the 100th position in the series AABABCABCDABCDE..... .....

I

Obviously __I__

Yes the answer is 'I'

This problem can be solved in two ways

1) by writing the sires and counting the respective number of the letter. But it doesn't workout in case of high numbers like 100.. or 1000

2)mathematically we can solve this problem.

The series can be treated as1+2+3+4+....

By the formula n(n+1)÷2 we get 13 terms are to be added to get 91 numbers

The remaining 9 alphabet are to be added to get 100th alphabet. Hence the nineth alphabet i is the 100th letter

Generally it is 1+2+3+4+....

Given 100th position..

When we add upto 13 terms..

1+2+3+4+5+6+7+8+9+10+11+12+13=91..

Remaining 9..

ABCDEFGHI..

Hence I is ans..

__H__

Can u tell us

__I__

__ABCDEF__