A die is thrown three times. Let X be ‘the number of twos seen’. Find the expectation of X.

Here, we have \[X\text{ }=\text{ }0,\text{ }1,\text{ }2,\text{ }3\] [Since, die is thrown \[3\] times]

And \[p\text{ }=\text{ }1/6,\text{ }q\text{ }=\text{ }5/6\]

Therefore, the required expression is \[1/2\].