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How many digits odd numbers greater than can be formed from the digits if Repetitions are not allowed:
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For greater than , the starting digit should be greater than or equal to , and for odd numbers, the ending digit will be .
Consider
6_ _ _ _ 5
The middle digits can be filled by remaining numbers in ways.
Similarly the ending digits can be
Hence total number of ways will be .
Similarly for8_ _ _ _5
Total number of ways will be ways.
Now if the starting digit is odd and greater than .
7_ _ _ _ 5 .
The ending digit can be only , other than . The middle digits can be filled by numbers is ways. Hence total number of permutations will be
.
Similarly for9_ _ _ _ 5 and so on.
Permutations will be .
Hence the required number of odd numbers greater than will be
.
Consider
The middle digits can be filled by remaining numbers in ways.
Similarly the ending digits can be
Hence total number of ways will be .
Similarly for
Total number of ways will be ways.
Now if the starting digit is odd and greater than .
The ending digit can be only , other than . The middle digits can be filled by numbers is ways. Hence total number of permutations will be
.
Similarly for
Permutations will be .
Hence the required number of odd numbers greater than will be
.
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Question Text | How many digits odd numbers greater than can be formed from the digits if Repetitions are not allowed: |
Answer Type | Text solution:1 |
Upvotes | 150 |