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 $years$)
$35$
$40$
$30$
$45$
Out of $30$ teachers of a school, a teacher of age $60$ $years$ retired. In his place another teacher of age $30$ $years$ was appointed. As a result, the mean age of the teachers will
In a $20$ over match, the required run rate to win is $7.2 .$ If the run rate is $6$ at the end of the $15^{th}$ over, the required run rate to win the match is
In a match, average of runs scored by five players is $49.$ It the runs scored by four players are $75,30,$ $63$ and $21$ respectively, then how many runs did the fifth player score?
The average age of $24$ boys and their teacher is $15 \,years.$ When the teacher's age is excluded, the average age decreases by $1\, year.$ The age of the teacher is in $years$ ?
A man covers $\frac{1}{3}$ of his journey by train at $80\, km / h ,$ next $\frac{1}{3}$ by $60\, km / h$ and the rest by bicycle at $30 \,km / h$. Find the average speed of the man during the whole journey. (in $km/h$)