$A$ rectangular block of metal has dimensions $21\, cm$, $77\, cm$, and $24\, cm$. The block is melted into a sphere. The radius of the sphere is .......... $cm$. (Take $\pi = \frac{22}{7}$)

It is required to design a circular pipe such that water flowing through it at a speed of $7 \ m/min$ fills a tank of capacity $440 \ m^3$ in $10 \ min$. The inner radius of the pipe should be (in $m$):

$A$ solid cylinder having a radius of base as $7 \, cm$ and length as $20 \, cm$ is bisected along its height to get two identical cylinders. What will be the percentage increase in the total surface area?

$X$ and $Y$ are two cylinders of the same height. The base of $X$ has a diameter which is equal to half the diameter of the base of $Y$. If the height of $X$ is doubled,the volume of $X$ becomes

$A$ hollow hemispherical bowl is made of silver with its outer radius $8\, cm$ and inner radius $4\, cm$. The bowl is melted to form a solid right circular cone of radius $8\, cm$. The height of the cone formed is......$cm$

$A$ cylindrical tank of diameter $35 \, cm$ is full of water. If $11$ litres of water is drawn off,the water level in the tank will drop by (in $cm$):