The radius of a wheel is $21 \, cm$. What is the distance (in $cm$) travelled by the wheel in $10$ revolutions?

The radius and height of a right circular cone are in the ratio $3: 4$. If its volume is $96\pi\, cm^3$,what is its slant height (in $cm$)?

The slant height of a right circular cone is $10 \, m$,and its height is $8 \, m$. Find the area of its curved surface (in $\pi \, m^2$).

What is the length (in metre) of the longest rod that can be placed in a room which is $2$ $metre$ long,$2$ $metre$ broad,and $6$ $metre$ high?

$A$ cubical metallic tank whose each edge measures $30\, cm$ is completely filled with water. If $2.7\, litres$ of water is taken out of it, what will be the depth of the remaining water in the tank? (in $cm$)

Water flows into a tank with a base of $150\, m \times 100\, m$ through a pipe with a cross-section of $2\, dm \times 1.5\, dm$ at a speed of $15\, km/h$. In what time will the water reach a depth of $3\, m$? (in $hours$)