10 digits
Level
pending
Find a 10-digit number where the first digit is how many zeros in the number, the second digit is how many 1s in the number etc. until the tenth digit which is how many 9s in the number. (The first digit being the one furthest to the left, the last digit being the units digit)
The answer is 6210001000.
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1 solution
I started out by saying the number was
0000000000
This has 10 zeros, but when we make the first digit a nine, it has nine zeros.
9000000000
But now there is a nine, so we keep re-writing the problem.
9000000001
8000000001
8000000010
8100000010
7100000010
7200000010
7210000010
7210000100
6210000100
6210001000
And this number works!