Question
A six-faced fair dice is rolled five times. The probability (in %) of obtaining “ONE” at least four times is
Options :
33.3
3.33
0.33
0.0033
Answer :
0.33
Solution :
A dice is rolled 5 times
n=5 7
P = (Probability of getting 1) = 1/6
q = 1- 1/6 = 5/6
Probability of getting 1 at least 4 times is
P(x ≥ 4) = P(x = 4) + P(x = 5)
= nC4p4qn-4 + nC5p5 qn-5
= nC4p4q1 + 5C5 p5 q0
= 5*(1/6)4(5/6)1 + 1*(1/6)5*(5/6)0
= 25/(6)5 + 1/(6)5 = 26/65 = 0.0033
% probability = 0.338%
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