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NCERT Class XI Mathematics - Probability - Solutions

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Question : 48
Total: 54
A die has two faces each with number ‘1’, three faces each with number ‘2’ and one face with number ‘3’. If die is rolled once, determine
(i) P(2)
(ii) P(1 or 3)
(iii) P(not 3)
Solution:  
Total number of faces in a die = 6
Number of faces with number 1 = 2
Number of faces with number 2 = 3
Number of faces with number 3 = 1
∴ P (1) =
2
6
 =
1
3
 , P (2) =
3
6
 =
1
2
 , P (3) =
1
6
(i) P (2) =
1
2
(ii) P (1 or 3) = P (1) + P (3) =
1
3
+
1
6
 =
2+1
6
 =
3
6
 =
1
2
(iii) P(not 3) = 1 - P(3) = 1 -
1
6
 =
5
6
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