2015 AMC 8 Problem 10

Below is the video solution and professionally curated solution for Problem 10 of the 2015 AMC 8, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2015 AMC 8 solutions, or check the answer key.

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Concepts:multiplication principledigits

Difficulty rating: 1070

10.

How many integers between 10001000 and 99999999 have four distinct digits?

3024 3024

4536 4536

5040 5040

6480 6480

6561 6561

Video solution:
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Written solution:

First, there are 99 digits to choose for the thousands digit since 00 can't be chosen.

Then, after that, there are 99 ways to choose the hundreds digit, 88 ways to choose the tens digit, and 77 ways to choose the ones digit. Therefore, we get 9987=45369\cdot9\cdot8\cdot7 = 4536 ways to choose such an integer.

Thus, the correct answer is B .

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