Monicaa Abhijit Solutions for Chapter: Mensuration-II (Solid Figures), Exercise 3: EXERCISE 18.3

A cylindrical road roller is of length $2 \mathrm{m}$ and diameter $84 \mathrm{cm}$. Find the number of revolutions it has to make to cover an area of $7,920 {\mathrm{m}}^2$.

[Take $\pi =\frac{22}{7}$]

The radii of two cylinders are in the ratio $3 : 4$ and their heights are in the ratio $5 : 3$. Find the ratio of their curved surface areas.

Some fruits are sliced and packed into cylindrical cans of height $32 \mathrm{cm}$ and diameter of base $20 \mathrm{cm}$. A label is placed around the curved surface of the can by leaving a margin of $2 \mathrm{cm}$ from the top and bottom of the can. Find the surface area of the label.

A school organized a competition of making and decorating pen holders in the shape of a cylinder by making its base and its curved surface area with cardboard. Each pen holder is supposed to have a radius of $3.5 \mathrm{cm}$ and height $10 \mathrm{cm}$. How much cardboard does the school need if $30$students are participating in the competition?

A metal pipe is $77 \mathrm{cm}$ long. The inner diameter of a cross-section is $4 \mathrm{cm}$, the outer diameter being $4.8 \mathrm{cm}$. Find its 

inner curved surface area

A metal pipe is $77 \mathrm{cm}$ long. The inner diameter of a cross-section is $4 \mathrm{cm}$, the outer diameter being $4.8 \mathrm{cm}$. Find its 

outer curved surface area

cA metal pipe is $77 \mathrm{cm}$ long. The inner diameter of a cross-section is $4 \mathrm{cm}$, the outer diameter being $4.8 \mathrm{cm}$. Find its 

total surface area 

A cylindrical vessel open at the top has a base diameter of $21 \mathrm{cm}$ and height $14 \mathrm{cm}$. Find the cost of tin plating its inner part at the rate of$₹5$  per $100 {\mathrm{cm}}^2$.