2015 AMC 8 Problems/Problem 10
How many integers between and have four distinct digits?
Video solution
https://youtu.be/Zhsb5lv6jCI?t=272
Solution
The question can be rephrased to "How many four-digit positive integers have four distinct digits?", since numbers between and are four-digit integers. There are choices for the first number, since it cannot be , there are only choices left for the second number since it must differ from the first, choices for the third number, since it must differ from the first two, and choices for the fourth number, since it must differ from all three. This means there are integers between and with four distinct digits.
See Also
2015 AMC 8 (Problems • Answer Key • Resources) | ||
Preceded by Problem 9 |
Followed by Problem 11 | |
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All AJHSME/AMC 8 Problems and Solutions |
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