Question 1133986: Find what percent of all four-digit numbers have repeated digits.
Answer by rothauserc(4718)   (Show Source):
You can put this solution on YOUR website! There are 9 * 10 * 10 * 10 = 9000 possible four-digit numbers. That is, 9 choices for the thousands digit, 10 each for the hundreds, tens, ones digits.
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Consider four-digit numbers with no repeats, there are
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9 * 9 * 8 * 7 = 4536 four-digit numbers with no repeats
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therefore, there are 9000 - 4536 = 4464 four-digit numbers with repeats
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4464/9000 = 0.496
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49.6 percent of all four-digit numbers have repeats
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