Question

The sum of the sigits in the unit place of all numbers formed with the help of 3,4,5,6 taken all at a time is

Answer 1

If the unit place is ‘3’ then remaining three places can be filled in 3! ways.
Thus ‘3’ appears in unit place in 3! times.
Similarly each digit appear in unit place 3! times.
So, sum of digits in unit place = 3!(3 + 4 + 5 + 6) = 18 x 6 = 108