- Joined
- 10 Dec 06
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31 Mar 21
@bigdoggproblem saidYeah, the 0 is considered a repeated digit in your example.
Do numbers like 1030 count? [two zeros, but not back-to-back]
31 Mar 21
2 edits
@joe-shmo saidEasiest approach to this is to find how many DON'T have a repeat.
How many integers between 1000 and 9999 inclusive have at least one repeated digit?
10x9x8x7=5040
9999-1000=8999
8999-5040=***3959***
31 Mar 21
@AThousandYoung
The method is right, but there are two errors in the arithmetic.
1)
There are 9999-1000+1 = 9000 total numbers (do not forget to count the number 1000 also).
2)
The thousands digit has only NINE possibilities; it cannot be 0. 9*9*8*7 = 4536
Solution:
9000 - 4536 = 4464