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Question
Choose the correct alternative :
X: is number obtained on upper most face when a fair die….thrown then E(X) = _______.
Options
3.0
3.5
4.0
4.5
Solution
X : number obtained on upper most face.
∴ Possible values of X are {1, 2, 3, 4, 5, 6}
∴ P(X = x) = `(1)/(6)`, for x = 1, 2, ..., 6
∴ E(X) = \[\sum\limits_{x=1}^{6} x\text{P}(x)\]
= `(1 xx 1)/(6) + (2 xx 1)/(6) + (3 xx 1)/(6) + (4 xx 1)/(6) + (5 xx 1)/(6) + (6 xx 1)/(6)`
= 3.5
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