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

Starting with $8000$ workers,the company increases the number of workers by $5 \%$,$10 \%$,and $20 \%$ at the end of the first,second,and third year,respectively. The number of workers in the fourth year is:

On a test consisting of $150$ questions,Rita answered $40 \%$ of the first $75$ questions correctly. What per cent of the other $75$ questions does she need to answer correctly for her grade on the entire exam to be $60 \%$?

$A$ $20 \%$ raise of price followed by a discount of $25 \%$ on the raised price will:

In $2009$,the food production was $5.5$ million tonnes and in $2010$,the production was $4.4$ million tonnes. Find out the percentage decrease in food production in these two years?

The population of a town was $160000$ three years ago. If it increased by $3 \%$,$2.5 \%$,and $5 \%$ respectively in the last three years,then the present population is: