If the radius of a circle is decreased by $20 \%$,then the percentage decrease in its area is (in $\%$)?

The dimensions of a field are $20 \text{ m}$ by $9 \text{ m}$. $A$ pit $10 \text{ m}$ long,$4.5 \text{ m}$ wide and $3 \text{ m}$ deep is dug in one corner of the field and the earth removed has been evenly spread over the remaining area of the field. What will be the rise in the height of the field as a result of this operation? (in $m$)

Two roads $XY$ and $YZ$ of $15 \ m$ and $20 \ m$ length respectively are perpendicular to each other. What is the distance between $X$ and $Z$ by the shortest route? (in $m$)

$A$ circular disc of area $0.49 \pi \, m^2$ rolls down a length of $1.76 \, km$. The number of revolutions it makes is:

$A$ wire when bent in the form of a circle encloses an area of $1386 \, cm^2$. What will be the enclosed area when the same wire is bent into the form of an equilateral triangle?

The circumference of a circular field is $440 \, m$. $A$ circular path of $10 \, m$ width runs around the outside of the field. Find the cost of gravelling the path at the rate of $70 \, \text{paise}$ per square metre? (in $Rs.$)