The average of $n$ numbers $x_{1}, x_{2}, \ldots, x_{n}$ is $x$. Then, the value of $\sum \limits_{i=1}^{n}\left(x_{i}-\bar{x}\right)$ is equal to

The average monthly salary of $20$ employees in an organisation is $Rs.\, 1500$. If the manager's salary is added, then the average salary increases by $Rs.\,100.$ What is the manager's monthly (in $Rs.$)

Ten years ago the average age of $P$ and $Q$ was $20\, years.$ Average age of $P, Q$ and $R$ is $30\, years$ now. After $10 \,years,$ the age of $R$ will be (in $years$)

The average of the price per $kg$ of rice at $10$ different places was $Rs.\, 4.85.$ After a week, the price per $kg.$ was increased by $20$ paise at $3$ places and decreased by $10$ paise at one place. The new average of price per $kg$ is in $Rs.$

Average temperature of first $4 \,days$ of a week is $38.6^{\circ} C$ and that of the last $4\, days$ is $40.3^{\circ} C$. If the average temperature of the week be $39.1^{\circ} C$, the temperature on $4^{th}$ day is. (in $^{\circ} C$)