Theory question 113
ProbabilityThe probabilities that Ali, Baba and Katty will gain admission to College are 2/3, 3/4 and 4/5 respectively. Find the probability that: (a) only Katty and Baba will gain admission. (b) none of them will gain admission. (c) at most two of them will gain admission.
Show the model answer
Model answer
(a) (1/3)(3/4)(4/5) = 1/5.
(b) (1/3)(1/4)(1/5) = 1/60.
(c) 1 − P(all three) = 1 − (2/3)(3/4)(4/5) = 1 − 2/5 = 3/5.
Explanation
'At most two' is everything except 'all three'.