There is six sides one a die. between 2 and 4 means 2, 3, and 4, which is 3 of the 6 sides. 3/6=1/2=0.5 the probability that the number of dots is between 2 and 4 is therefore 1/2 or 50%. but one thing, it says the average, meaning add up what you got on all 30 rolls and dividing it by 30, and by probability the average number would be between 3 and 4, to be specific it would be 3.5, which is between 2 and 4. with that the probability is basically 100%, but I believe you messed up the question somewhere and meant the probability the number of dots is between 2 and 4, not average. If its the probability the average number is between 2 and 4 then the answer is theoretically 100%, If you are asking the probability the dice will roll between 2 and 4 (note its not average of 30) then it is 50%. Hope this helps.
