The average marks obtained by $150$ students in an examination is $40$. If the average marks of passed students is $60$ and that of the failed students is $20$,what is the number of students who passed the examination?

The average weight of a class of $24$ students is $35 \, kg$. If the weight of the teacher is included, the average weight increases by $400 \, g$. The weight of the teacher is (in $kg$):

The average monthly salary of all the employees in an industry is $Rs. 12,000$. The average salary of male employees is $Rs. 15,000$ and that of female employees is $Rs. 8,000$. What is the ratio of male employees to female employees?

The average marks obtained by a class of $60$ students is $65$. The average marks of half of the students is found to be $85$. The average marks of the remaining students is:

An aeroplane travels $2500 \, km$,$1200 \, km$,and $500 \, km$ at $500 \, km/h$,$400 \, km/h$,and $250 \, km/h$ respectively. The average speed is (in $km/h$):

Visitors to a show were charged $Rs. 15$ each on the first day,$Rs. 7.50$ on the second day,$Rs. 2.50$ on the third day,and the total attendance on the three days was in the ratio $2:5:13$ respectively. The average charge per person for the entire three days is (in $Rs.$):