flash
Probability
Level
2
how many four digit number are there with no digit repeated
The answer is 4536.
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1 solution
there are 10 digits including 0 no of four digit nos in which the digits are not repeated is equal to filling up of four places in a row 0000 the first place can be filled up in 9 ways, as 0 cannot be placed the second plce can be filled in 9 ways as 0 can be used the third place can be filled in 8 ways the fourth place can be filled up in 7 ways hence total no of ways is 9x9x8x7 = 4536