enak wrote:

A number N is formed by placing first 100 integers in order (N= 1234567891011121314.......). If N is a 150 digit number, what is the remainder when N is divided by 10?

(A) 1

(B) 3

(C) 7

(D) 8

(E) 9

What we need is to figure out is the 150th digit of the integer N!

So, if 9 digits(1-9) are consumed by one-digit numbers,

every set of 10 numbers(eg 10-19) will consume 20 more places in N.

Positions 10-29 will be occupied by 10-19

Positions 30-49 will be occupied by 20-29

Positions 50-69 will be occupied by 30-39

Positions 70-89 will be occupied by 40-49

Positions 90-109 will be occupied by 50-59

Positions 110-129 will be occupied by 60-69

Positions 130-149 will be occupied by 70-79

Therefore, the 150th digit is

8(Option D), which is also the remainder when N is divided by 10

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