Theory question 105
ProbabilityThe probabilities of Rotey obtaining the highest mark in Mathematics, Physics and Biology tests are 0.9, 0.75 and 0.8 respectively. Calculate the probability of getting the highest marks in at least two subjects.
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Model answer
All three: 0.9 × 0.75 × 0.8 = 0.54
M, P not B: 0.9 × 0.75 × 0.2 = 0.135
M, B not P: 0.9 × 0.25 × 0.8 = 0.18
P, B not M: 0.1 × 0.75 × 0.8 = 0.06
At least two = 0.915
Explanation
'At least two' means exactly two or all three.