面積與體積

In the figure, $OAB$ is a sector of radius $r\text{ cm}$. If $\angle AOB=120^\circ$ and the area of the sector is $12\pi\text{ cm}^2$, then $r=$

In the figure, the rectangle $ABCD$ is divided into eight identical rectangles. Find the area of the rectangle $ABCD$.

The figure shows a solid right circular cone of height $12\text{ cm}$. The circumference of the base is $18\pi\text{ cm}$. Find the total surface area of the circular cone.

In the figure, the volume of the right prism is

In the figure, $OAB$ and $OCD$ are sectors with centre $O$. It is given that the area of the shaded region $ABDC$ is $54\pi\text{ cm}^2$. If $AC=6\text{ cm}$, then $OA=$

In the figure, $OAB$ is a sector with centre $O$. If the perimeter of the sector $OAB$ is $12\text{ cm}$, find $OA$ correct to the nearest $0.01\text{ cm}$.

In the figure, the volume of the right prism is

If a solid metal hemisphere of radius $r$ is melted and recast into $3$ identical solid right circular cones of height $h$ and base radius $r$, then $r:h=$

In the figure, the area of the trapezium $ABCD$ is

In the figure, the solid consists of a hemisphere of radius $3\text{ cm}$ joined to the bottom of a right circular cylinder of height $8\text{ cm}$ and base radius $3\text{ cm}$. Find the volume of the solid.