Q. 55.0( 1 Vote )

How many 4-digit

Answer :

Let Suppose 4 digit number as 4 boxes as shown below.First Box is at 1000thplace, the Second box is at 100th place, the Third box is at 10th place, and Fourth box is at 1st place.


The 1st box can be filled with four numbers(2, 3, 4, 5) if we include 0 in the 1st box then it becomes 3 digit number(i.e. 0234 is 3 digit number, not 4 digits)


The 2nd box can be filled with five numbers(0, 2, 3, 4, 5) as repetition is allowed.


Similarly, the 3rd box can be filled with five numbers(0, 2, 3, 4, 5) as repetition is allowed.


Similarly, the 4th box can be filled with five numbers(0, 2, 3, 4, 5) as repetition is allowed.


Total number of ways is 4 × 5 × 5 × 5 = 500


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