The average marks obtained in a class of $50$ students is $70 \%$. The average of the first $25$ students is $60 \%$ and that of the next $24$ students is $80 \%$. What is the percentage of marks obtained by the last student?

If $A$'s salary is $20\%$ higher than $B$'s,then how much percent is $B$'s salary less than $A$'s salary?

Two litres of water evaporate from $10$ litres of a solution containing $10 \%$ salt. The percentage of salt in the remaining solution is

The value of a machine is $Rs$ $6250$. It decreases by $10 \%$ during the first year,$20 \%$ during the second year,and $30 \%$ during the third year. What will be the value of the machine after $3$ years?

In the month of January,the Railway Police caught $4,000$ ticketless travellers. In February,the number rose by $5\%$. However,due to constant vigil by the Police and the Railway staff,the number reduced by $5\%$ in March and in April it further reduced by $10\%$. The total number of ticketless travellers caught in the month of April was:

Three sets of $40, 50,$ and $60$ students appeared for an examination,and the pass percentages were $100\%, 90\%,$ and $80\%,$ respectively. The pass percentage of the whole set is: