Find the lateral surface area of a cube with an edge length of $15 \, cm.$ (in $cm^{2}$)

The length,breadth,and height of a cuboid are $20\, cm$,$15\, cm$,and $12\, cm$ respectively. Find its total surface area (in $cm^2$).

The front compound wall of a house is decorated by wooden spheres of diameter $21\, cm,$ placed on small supports as shown in the figure. Eight such spheres are used for this purpose,and are to be painted silver. Each support is a cylinder of radius $1.5\, cm$ and height $7\, cm$ and is to be painted black. Find the cost of paint required if silver paint costs $25$ paise per $cm^{2}$ and black paint costs $5$ paise per $cm^{2}.$

Find the amount of water displaced by a solid spherical ball of diameter $4.2 \, cm$,when it is completely immersed in water. (in $, cm^3$)

The ratio of radii of two cylinders with equal height is $4:5$. What is the ratio of their volumes?

Two cubes each of $8 \, cm$ edge are joined end to end. Find the total surface area of the cuboid so formed (in $cm^{2}$).