$A$ person spends $25 \%$ of his annual income on house rent,$15 \%$ on education of children,and $45 \%$ on other items. If he saves $₹ 14,400$ annually,then the person's total income is: (in $,000$)

Sonu invested $10 \%$ more than Mona. Mona invested $10 \%$ less than Raghu. If the total sum of their investments is ₹$5,780$,how much amount did Raghu invest?

If an electricity bill is paid before the due date,one gets a reduction of $4 \%$ on the amount of the bill. By paying the bill before the due date,a person got a reduction of $₹ 13$. The amount of his electricity bill was:

$A$ number $x$ is $125 \%$ of $y$. To compute $y$,the number $x$ has to be multiplied by:

$5 \%$ of $(25 \%$ of $₹ 1600)$ is

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?