Question

what will be the sum of adding all possible four digit numbers formed by 7,9,1,3 using each of the digits only once?

Answer 1

our digit numbers =4⋅3⋅2⋅1=24

=

4

⋅

3

⋅

2

⋅

1

=

24

ways we can form a four digit number. Since it's a 4 digit number, each digit will appear 6=24/4

6

=

24

/

4

times in each of units, tens, hundreds, and thousands place. Therefore, the sum of digits in the units place is 6(1+2+5+6)=84

6

(

1

+

2

+

5

+

6

)

=

84

.

Why they are adding 1+2+5+6

1

+

2

+

5

+

6

?

Similarly sum of digits at tens,hundreds,thousands place is 84

84

Required sum of all numbers =84+84⋅10+84⋅100+84⋅1000=93324

Answer 2

bhai yiska too muje bhi nahi pata aagar tuje mila too muje bhi bata Dena..