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(20 points) We have four urns. Urn 1 contains one green ball, and one red ball.

ID: 3044609 • Letter: #

Question

(20 points) We have four urns. Urn 1 contains one green ball, and one red ball. Urn 2 contains one green ball and two red balls. Urn 3 contains one green ball and three red balls. Urn 4 contains one green ball and 4 red balls. First, we select an urn. The probability we select Urn 1 is 1/10, the probability we select urn 2 is 2/10, the probability we select urn 3 is 3/10, and the probability we select urn 4 is 4/10. Then we select a ball at random from the selected urn. What is the probability the ball is red 5.

Explanation / Answer

P(ball is red)=P(urn 1 and red+urn 2 and red+urn 3 and red+urn 4 and red)

=(1/10)*(1/2)+(2/10)*(2/3)+(3/10)*(3/4)+(4/10)*(4/5)=0.7283