In expressing a length $81.472 \, km$ as nearly as possible with three significant digits,find the percentage error?

The average salary of male employees in a firm was $Rs$ $5200$ and that of females was $Rs$ $4200$. The mean salary of all the employees was $Rs$ $5000$. What is the percentage of female employees?

$A$ person scores $45 \%$ of the total marks in the exam and still fails by $40$ marks. The passing percentage of the exam is $55 \%$. What is the maximum marks of the exam?

An army lost $10 \%$ of its men in war,$10 \%$ of the remaining due to diseases,and $10 \%$ of the rest were hurt. Thus,the strength was reduced to $729000$ active men. Find the original strength.

If $x$ is $80 \%$ of $y$,then what percent of $2x$ is $y$?

Mrs. Jain invests $14 \%$ of her monthly salary,i.e.,$Rs. 7014$ in Insurance Policies. Later she invests $21 \%$ of her monthly salary on Family Mediclaim Policies; also she invests another $6.5 \%$ of her salary on Mutual Funds. What is the total annual amount invested by Mrs. Jain?