Tree diagram for two rolls of an eight-sided die and a binomial count of how often exactly one multiple of four occurs

Tree diagram for two rolls of an eight-sided die and a binomial count of how often exactly one multiple of four occurs

12 marks

A fair eight-sided die has faces numbered \(1\) to \(8\). The die is rolled twice. Let \(M\) be the event that the score on a roll is a multiple of \(4\).

  1. Copy and complete the tree diagram below, which shows the possible outcomes of the two rolls.[3]
______
\(M\)
______
\(M'\)
______
\(M\)
______
\(M'\)
______
\(M\)
______
\(M'\)
First roll
Second roll

Let \(E\) be the event that exactly one of the two rolls gives a multiple of \(4\).

  1. Find \(\mathrm{P}(E)\).[3]

The die is rolled twice on each of \(6\) separate turns.

  1. Find the probability that \(E\) occurs on exactly \(3\) of the \(6\) turns.[3]
  2. Find the probability that \(E\) occurs on at least \(3\) of the \(6\) turns.[3]

Solution:

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Answer:(a) every \(M\) branch \(\dfrac14\), every \(M'\) branch \(\dfrac34\) (b) \(\dfrac38\) (c) \(0.257\) (d) \(0.404\)

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