Question 10: Writing a sequence of natural numbers from 1 to 999, we get a natural number A. How many times is the digit 0 written?

In the sequence (2) the digit 0 is present 300 times.

Compared with sequence (1), in sequence (2) we write more 0’s:

Enter the hundreds 100 times (the hundreds digit of numbers from 000 to 099);
Into tens 10 times (tens digit of numbers 000 through 009);
Enter the units row once (the units digit of 000).

So the digit 0 in the sequence (1) is written as: 300 – 111 = 189 (times).