4124 You roll a cube numbered from Ito 6 What is the probabi

4.124 You roll a cube numbered from Ito 6. What is the probability that the number observed is a or 2? 4.128 A jar contains 4 green. 16 white, and 8 brown marbles. A marble is drawn at random. What is the probability that the marble is not green? 4.129 Ajar contains 18 green. 8 navy. 5 gray, and 5 blue marbles. A marble is drawn at random. Find P(not gray).

Solution

4.124)

Total numbers = 6

Probability of getting a one = 1/6

Probability of getting a two = 1/6

Probability of number observed being 1 or 2 = Probability of getting a one + Probability of getting a two

= 1/6 + 1/6

= 2/6

= 1/3

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4.128) Total marbles = 4 + 16 + 8 = 28

Probability of drawing a green marble = No of green marbles/total marbles = 4/28 = 1/7

Probability of not drawing a green marble = 1 - Probability of drawing a green marble

                                                                     = 1 - 1/7 = 6/7 = 0.857

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4.129)

Total marbles = 18 + 8 + 5 + 5 = 36

Probability of drawing a gray marble = No of gray marbles/total marbles = 5/36

Probability of not drawing a gray marble = 1 - Probability of drawing a gray marble

                                                                     = 1 - 5/36 = 31/36 = 0.861