How many numbers are there between 100 and 1000 in which all the digit

1.	How many numbers are there between 100 and 1000 in which all the digits are distinct.
Answer» Between hundred and thousand means that we want to find the number of distinct 3 digit numbers .1st: hundredth place can be filled with any one of the 9 digits (except 0).2nd: tenth place can be filled with any one of the 9 digits remaining (including 0). 3rd :unit\'s place can be filled with any one of the remaining 8 digits. Therefore total number of 3 digits numbers with distinct digits is =9×9×8 =648.

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