The mean weight of $150$ students in a class is $60 \,kg.$ The mean weight of boys is $70\, kg$ and that of girls is $55 \,kg$. What is the number of boys in the class?
$50$
$60$
$75$
$100$
The average weight of $8$ persons increases by $2.5\, kg$ when a new person comes in place of one of them weighing $65\, kg$. What might be the weight of the new person? (in $kg$)
There are $35$ students in a hostel. If the number of students increased by $7,$ the expenses of the mess were increased by $Rs.\,42$ per $day$ while the average expenditure per head decreased by $Rs.\,1$, Find out the actual expenditure of the mess. (in $Rs.$ )
Last year, $5$ companies had an average of $16$ non working days each, and $2$ companies had $5$ fewer non working days each. What was the average number of non working days given by the same companies this $year$ ?
The mean daily profit made by a shopkeeper, in a month of $30\, days,$ was $Rs.\,350.$ If the mean profit for the first $15\, days$ was $Rs.\, 275,$ then the mean profit for the last $15\, days$ would be (in $Rs\,$)
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 $Rs.$)