A six sided unbiased die with four green faces and two red faces is rolled…

2018

A six sided unbiased die with four green faces and two red faces is rolled seven times. Which of the following combinations is the most likely outcome of the experiment?

Answer: C. Five green faces and two red faces.Key idea: Use the binomial distribution with n = 7 trials and probability of green p = 4/6 = 2/3. Step 1: Probability of exactly k green faces is P(k) =…

  1. A.

    Three green faces and four red faces.

  2. B.

    Four green faces and three red faces.

  3. C.

    Five green faces and two red faces.

  4. D.

    Six green faces and one red face.

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Correct answer: C

Key idea: Use the binomial distribution with n = 7 trials and probability of green p = 4/6 = 2/3.

  • Step 1: Probability of exactly k green faces is P(k) = C(7,k)*(2/3)^k*(1/3)^(7-k).

  • Step 2: The mode of a binomial distribution is floor((n+1)p). Here (n+1)p = 8*(2/3) = 16/3, so the mode is floor(16/3) = 5. Thus five green faces is the most likely count.

  • Step 3: Compare the probabilities for the outcomes in the choices (using 3^7 = 2187 so (2/3)^k*(1/3)^(7-k) = 2^k / 2187):

    • Three green, four red: P = C(7,3)*2^3/2187 = 35*8/2187 = 280/2187 ≈ 0.128.

    • Four green, three red: P = C(7,4)*2^4/2187 = 35*16/2187 = 560/2187 ≈ 0.256.

    • Five green, two red: P = C(7,5)*2^5/2187 = 21*32/2187 = 672/2187 ≈ 0.307.

    • Six green, one red: P = C(7,6)*2^6/2187 = 7*64/2187 = 448/2187 ≈ 0.205.

Conclusion: Five green faces and two red faces is the most likely outcome, with probability 672/2187 ≈ 0.307.

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