2004 AMC 8 Problems/Problem 2
Contents
Problem
How many different four-digit numbers can be formed by rearranging the four digits in ?
Solution 1
We can solve this problem easily, just by calculating how many choices there are for each of the four digits. First off, we know there are only choices for the first digit, because isn't a valid choice, or the number would a 3-digit number, which is not what we want. We have choices for the second digit, since we already used up one of the digits, and choices for the third, and finally just choices for the fourth and final one. is 12, but there are 2 zeros that have been counted as different numbers, so divide by 2 to get .
Solution 2
Note that the four-digit number must start with either a or a . The four-digit numbers that start with are , and . The four-digit numbers that start with are , and which gives us a total of .
See Also
2004 AMC 8 (Problems • Answer Key • Resources) | ||
Preceded by Problem 1 |
Followed by Problem 3 | |
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All AJHSME/AMC 8 Problems and Solutions |
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