1. How many of them contain at least one '1'?
2. If I wrote them out in one long line, how many 1 digits would there be?

for part 1, it's definitely not 20,000,000,000.  For example, from 1 to 1,000, there are 272 numbers that contain at least one 1's.

I agree with the rest of the people's solutions..

I got the following formula for part 1:
for any positive integer n, there are
10ⁿ(1-.9ⁿ)+1
numbers from 1 to 10ⁿ that contains at least one digit of 1.

i hope i am doing this right.. o_O"

Posted by saddi Sandy on 2004-07-30 08:01:03