InterviewSolution
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Find the number of integers greater than 7000 that can be formed with the digits 3, 5, 7, 8 and 9 where no digits are repeated. |
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Answer» We have to find the number of integers greater than 7000 with the digits 3,5, 7, 8 and 9. So, with these digits, we can make maximum five-digit numbers because repetition is not allowed. Since all the five-digit numbers are greater than 7000, we have Number of five-digit integers = 5 x 4 x 3 x 2 x 1 = 120 A four-digit integer is greater than 7000 if thousandth place has any one of 7, 8 and 9. Thus, thousandth place can be filled in 3 ways. The remaining three places can be filled from remaining four digits in 4P3 ways. So, total number of four-digit integers = 3x 4P3 = 3 x 4 x 3 x 2 = 72 Total number of integers = 120 + 72 = 192 |
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