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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