If $75 \%$ of a number is added to $75$,the result is the number itself. The number is:

$A$ village lost $12 \%$ of its goats in a flood and $5 \%$ of the remainder died from diseases. If the number left now is $8360$,what was the original number before the flood?

Rita invested $25 \%$ more than Sunil. Sunil invested $30 \%$ less than Abhinav who invested $Rs. 6000$. What is the respective ratio between the amount that Rita invested and the total amount invested by all of them together?

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?

$A$ student multiplied a number by $\frac{3}{5}$ instead of $\frac{5}{3}$. What is the percentage error in the calculation (in $\%$)?

$65 \%$ of $? = 20 \%$ of $422.50$