3 A fair 8 -sided dice has faces labelled 10, 20, 30, ..., 80 .
- State the distribution of the score when the dice is rolled once.
- Write down the probability that, when the dice is rolled once, the score is at least 40 .
- The dice is rolled three times.
- Find the variance of the total score obtained.
- Find the probability that on one of the rolls the score is less than 30 , on another it is between 30 and 50 inclusive and on the other it is greater than 50 .