The diameters of two concentric circles are $8\, cm$ and $10\, cm$. The area of the region between them is

If all the sides of a triangle are increased by $200 \%$,then the area of the triangle will increase by (in $\%$):

Two sides of a plot measure $32 \ m$ and $24 \ m$ and the angle between them is a perfect right angle. The other two sides measure $25 \ m$ each. The area of the plot in $m^{2}$ is:

If the radius of a circle is increased by $75 \%,$ then its circumference will increase by (in $\%$)

Each side of a rhombus is $26 \ cm$ and one of its diagonals is $48 \ cm$ long. The area of the rhombus is (in $cm^2$)

$A$ drawing room is $7.5 \text{ m}$ long,$6.5 \text{ m}$ broad,and $6 \text{ m}$ high. Find the length of paper $2.5 \text{ dm}$ wide required to cover its walls,allowing $8 \text{ m}^2$ for doors.