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Question
The number of 4 digited numbers that can be formed using the digits 2, 4, 5, 7,8 when repetition is not allowed
The number of 4 digited numbers that can be formed using the digits 2, 4, 5, 7,8 when repetition is not allowed
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Solution
4 digits __ __ __ __
Now the first digit can be filled by any of the 5 numbers. Therefore there are 5 possibilities
The second digit will have only 4 possibilities as one of the numbers gets used up by the 1st digit.
Similarly the 3rd and 4th digits will have 3 and 2 possibilities respectively.
Therefore no.of 4 digit numbers that can be formed are 5 x 4 x 3x 2 = 120
Now the first digit can be filled by any of the 5 numbers. Therefore there are 5 possibilities
The second digit will have only 4 possibilities as one of the numbers gets used up by the 1st digit.
Similarly the 3rd and 4th digits will have 3 and 2 possibilities respectively.
Therefore no.of 4 digit numbers that can be formed are 5 x 4 x 3x 2 = 120
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