Question

What will be the sum of adding all the possible four-digit numbers formed by7 , 9, 1 , 3 using each of the digits only once?
(1) 133220
(2) 122320
(3) 133230
(4) 133320
(Hint: Each of the given digits will occur six times in the units place and there will be 4 groups of 6 numbers each.]
I will mark brainlist for correct answer ​

Answer 1

Answer:

Four digit numbers =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 times in each of units, tens, hundreds, and thousands place. Therefore, the sum of digits in the units place is 6(7+9+1+3)=120.

Similarly sum of digits at tens,hundreds,thousands place is 120

Required sum of all numbers =120+120⋅10+120⋅100+120⋅1000=133320

Therefore answer is : C. 133320

Hope this helps