If $\mu$ is the mean of a distribution $(y_i, f_i)$,then $\sum f_i(y_i - \mu) = $

The mean of $50$ observations is $36$. If two observations $30$ and $42$ are removed,what is the mean of the remaining observations?

The median of a set of $13$ observations which are in decreasing order is $18.6$. If the first two observations are increased by $1$ and the last three observations are decreased by $5$,then the median of the set of new observations is-

The median of a set of $19$ observations is $30$. If two observations with values $8$ and $32$ are added,what is the median of the new set of $21$ observations?

The mean of discrete observations $y_1, y_2, \ldots, y_n$ is given by:

If a man spends an equal amount of money to buy three types of pens at $5$ Rs/pen,$10$ Rs/pen,and $20$ Rs/pen,what is the average cost per pen?