A die is thrown twice. What is the probability that (i) 5 will not come up either time? (ii) 5 will come up at least once?

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asked Jul 24, 2017 in Mathematics by sforrest072 (157,439 points) 63 447 1243

1 Answer

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answered Jul 24, 2017 by vikash (21,277 points) 4 21 73
 
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Answer:

(i) Consider the following events.
A = first throw shows 5,
B = second throw shows 5
P(A) = 6/36, P(B) = 6/36 and P(notB) = 5/6
⇒ P(notA) = 1– 6/36 = 30/36 = 5/6
Required probability = 5/6 × 5/6 = 25/36

(ii) Number of events when 5 comes at least once = 11
Probability = 11/36

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