Question

In the arcade game Skee Ball, players roll a ball up a ramp and receive 10 to 50 points based on where the ball lands. Players will attempt to aim the ball to receive higher scores, which are more difficult to achieve based on size and location. However, if a ball is rolled randomly up the ramp, the probabilities of the ball landing in different scoring areas are not equal. Assume the following probabilities for each possible score:

Score 10 Points 20 Points 30 Points 40 Points 50 Points
Probability 0.50 0.25 0.15 0.07 0.03

Assume that a player rolls three balls at random.

Required:
a. What is the probability of a total score of at least 100 points?
b. If the first ball scores 30 points, what is the probability of a total score of at least 100 points?
c. Are the events "the first ball scores 30" and the "total score is at least 100" independent? Why or why not??
d. What is the expected total score? What is the variance of the score on one roll?

Answer 1

Explanation:

a) sum of 100 can be achieved from following set of score

10,40,50. This score can be achieved in 3! ways

20,30,50. This score can be achieved in 3! ways

20,40,40. This score can be achieved in 4 ways

30,30,40. This score can be achieved in 4 ways

So,

P(score of 100)=