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The mean of the numbers obtained on throwing a die having written 1 on three faces, 2 on two faces and 5 on one face is
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The mean of the numbers obtained on throwing a die having written 1 on three faces, 2 on two faces and 5 on one face is

A. 1

B. 2

C. 5

D. 8 / 3

Solution:

B. 2

Explanation:

A dice with the numbers 1 on three faces, 2 on two faces, and 5 on one face is given. Let X represent a random variable that represents a number on a die.

Then X can have any value between 1 and 5.

There are a total of six numbers.

Now

herefore

xpectation of X \mathrm{E}(\mathrm{X}):

\mathrm{E}(\mathrm{X})=\sum_{\mathrm{i}=1}^{\mathrm{n}} \mathrm{x}_{\mathrm{i}} \mathrm{p}_{\mathrm{i}}

Now by substituting the values we get =1 \times \frac{1}{2}+2 \times \frac{1}{3}+5 \times \frac{1}{6}

=\frac{1}{2}+\frac{2}{3}+\frac{5}{6}=\frac{3+4+5}{6}=\frac{12}{6}

\Rightarrow \mathrm{E}(\mathrm{X})=2

As a result, the correct answer is (B).

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