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प्रश्न
Serial numbers for an item produced in a factory are to be made using two letters followed by four digits (0 to 9). If the letters are to be taken from six letters of English alphabet without repetition and the digits are also not repeated in a serial number, how many serial numbers are possible?
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उत्तर
Number of ways of selecting the first letter = 6
Number of ways of selecting the second letter = 5
(as repetition of letters is not allowed)
Number of ways of selecting the digit in the third place = 10
Number of ways of selecting the digit in the fourth place = 9
(as repetition of digits is not allowed)
Number of ways of selecting the digit in the fifth place = 8
Number of ways of selecting the digit in the sixth place = 7
Possible serial numbers=`6xx5xx10xx9xx8xx7=151200`
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