# Advent calendar 2020

## 14 December

The numbers 33, 404 and 311 contain duplicate digits. The numbers 120, 15 and 312 do not.

How many numbers between 10 and 999 (inclusive) contain no duplicate digits?

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The numbers 33, 404 and 311 contain duplicate digits. The numbers 120, 15 and 312 do not.

How many numbers between 10 and 999 (inclusive) contain no duplicate digits?

Not Roman numerals

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