The number of 4-digit numbers possible using 1,1,2, and 4 is
4!
2!
=12 Number of 1′s,2′sand4′s in units digits will be in the ratio 2:1:1, i.e. 61′s,32′sand34′s. Sum =6(1)+3(2)+3(4)=24 Similarly, in tens digit, hundreds digit and thousands digit as well. Therefore, sum =24+24(10)+24(100)+24(1000)=24(1111) Mean =