1.  3.5
   2.  91/36 or 2.5278
   3.  49/24 or 2.0417

Q.3. Total number of ways 3 dice can fall = 63 = 216
     Number of ways with no score under 2 = 53 = 125
         So number with 1 as least score = 63 - 53 = 91
  Similarly number with 2 as least score = 53 - 43 = 61 
            number with 3 as least score = 43 - 33 = 37 
            number with 4 as least score = 33 - 23 = 19
            number with 5 as least score = 23 - 13 =  7 
            number with 6 as least score = 13 - 03 =  1
  So average of least scores =
   (91*1 + 61*2 + 37*3 + 19*4 + 7*5 +1*6)/216 = 441/216 etc.