$A$ well,$20 \, m$ deep,is $7 \, m$ in radius. Find the cost of cementing the inner curved surface at the rate of ₹ $15$ per $m^2$. (in ₹)

$A$ pyramid is a solid figure,the base of which is

Shanti Sweets Stall was placing an order for making cardboard boxes for packing their sweets. Two sizes of boxes were required. The bigger of dimensions $25 \,cm \times 20 \,cm \times 5 \,cm$ and the smaller of dimensions $15 \,cm \times 12 \,cm \times 5 \,cm$. For all the overlaps,$5\%$ of the total surface area is required extra. If the cost of the cardboard is $Rs. 4$ for $1000 \,cm^2$,find the cost of cardboard required for supplying $250$ boxes of each kind.

Find the lateral or curved surface area of a closed cylindrical petrol storage tank that is $4.2\, m$ in diameter and $4.5\, m$ high. $\left[\text{Assume } \pi = \frac{22}{7}\right]$ (in $, m^2$)

The radius and volume of a cylinder are $3.5\,cm$ and $2310\,cm^3$ respectively. Find its height in $cm$.

In the Indus Valley Civilisation (about $3000\, B.C.$),the bricks used for construction work had dimensions in the ratio: