S.chand Class 8 Maths Solution Chapter 17 Volume and Surface Area of Solids Exercise 17 D

 Exercise 17 D

Question 1

1. Information about a few cylinders is given below. Copy and complete the table. $\left(\pi=\frac{22}{7}\right)$

	Radius (cm)	Height (cm)	Curved Surface	Area of the base	Whole surface
(a)	7	6
(b)	14	10
(c)	21	5
(d)	$10 \frac{1}{2}$	16

2. Copy and complete the table. $\left(\pi=\frac{22}{7}\right)$.

	(a)	(b)	(c)	(d)
Curved Surface $(cm^2)$	704	3960	1320	24200
Radius (cm)	?	15	?	35
Height (cm)	8	?	14	?

In the following problems, take $\pi=\frac{22}{7}$ if not mentioned otherwise.

3. The circumference of the base of a right circular cylinder is $220 \mathrm{~cm}$. If the height of the cylinder is $2 \mathrm{~m}$, find the lateral surface area of the cylinder.

4. Aclosed circular cylinder has diameter $20 \mathrm{~cm}$ and height $30 \mathrm{~cm}$. Find the total surface area of the cylinder. $(\pi=3.14)$

5. A cylindrical pillar is $1 \mathrm{~m}$ in diameter and $4.2 \mathrm{~m}$ in height. Find the cost of white washing the curved surface of the pillar at the rate of $₹ 15$ per $\mathrm{m}^{2}$.

6. Find the height of the solid circular cylinder of total surface area $660 \mathrm{~cm}^{2}$ and radius $5 \mathrm{~cm}$.

[Hint. $2 \pi r^{2}+2 \pi r h=660 \Rightarrow 2 \pi r(r+h)=660$

$\left.\Rightarrow 2 \times \frac{22}{7} \times 5 \times(5+h)=660 \Rightarrow 5+h=\frac{660 \times 7}{2 \times 22 \times 5}=21\right]$

7. The inner diameter of a circular well is $4.2 \mathrm{~m}$. It is $12 \mathrm{~m}$ deep. Find (i) its inner curved surface area (ii) the cost of plastering the inner curved surface at the rate of $₹ 50$ per $\mathrm{m}^{2}$.

8. A metal pipe is $77 \mathrm{~cm}$ long, the inner diameter of the cross-section is $4 \mathrm{~cm}$ and the outer diameter is $4.8 \mathrm{~cm}$. Find the (i) inner curved surface area (ii) outer curved surface area (iii) total surface area.

9. A hollow cylindrical pipe has inner circumference $44 \mathrm{dm}$ and outer $45 \mathrm{dm}$. Find the cost of painting it from both sides (inside as well as outside) at $₹ 2$ per $\mathrm{m}^{2}$ if length is $3.5 \mathrm{~m}$.