Q. What is the sum of all the four digit numbers which are formed by the digits 1,2,5,6 when each digit is used only once in formed number
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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(1+2+5+6)=84.
Why they are adding 1+2+5+6?
Similarly sum of digits at tens,hundreds,thousands place is 84
Required sum of all numbers =84+84⋅10+84⋅100+84⋅1000=93324
Mark it as brainliest
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