First slide
Permutations
Question

There are 720 permutations of the digits 1, 2, 3, 4, 5, 6. Suppose these permutations are arranged from smallest to largest numerical values, beginning from 1 2 3 4 5 6 and ending with 6 5 4 3 2 1 Then the digit in unit place of number at 267Tth position is ________ .

Moderate
Solution

Number of numbers beginning with 1=120                                                                  

1     

Number of numbers beginning with 2=120                                                                 

2     

Starting with 31 ………………………………=24

31    

Starting with 3214 …………………………….=2

3214  

Finally                                                               = 1
                                                                              

321546

                                                               
Hence, unit place digit of 267th number is 6.

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