NCERT Class XI Mathematics - Probability - Solutions

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Question : 21
Total: 54
Three coins are tossed. Describe
(i) Two events which are mutually exclusive.
(ii) Three events which are mutually exclusive and exhaustive.
(iii) Two events, which are not mutually exclusive.
(iv) Two events which are mutually exclusive but not exhaustive.
(v) Three events which are mutually exclusive but not exhaustive.
Solution:  
An experiment consists of tossing three coins then the sample space S is S = {HHH, HHT, HTH, HTT, THH, THT, TTH, TTT}
(i) Two events A and B which are mutually exclusive are
A : “getting atmost one head” and
B : “getting atmost one tail”
(ii) Three events A, B and C which are mutually exclusive and exhaustive are
A : “getting atleast two heads”
B : “getting exact two tails” and
C : “getting exactly three tails”
(iii) Two events A and B which are not mutually exclusive are
A : “getting exactly two tails” and
B : “getting atmost two heads”
(iv) Two events A and B which are mutually exclusive but not exhaustive are
A : “getting atleast two heads” and
B : “getting atleast three tails”
(v) Three events A, B and C which are mutually exclusive but not exhaustive are
A : “getting atleast three tails”
B : “getting atleast three heads”
C : “getting exactly two tails”
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