Selina Solutions Concise Maths Class 8 Chapter 21: Surface Area, Volume and Capacity

Selina Solutions Concise Maths Class 8 Chapter 21 Surface Area, Volume and Capacity consists of accurate answers to the problems present in the textbook. Each and every problem is solved with utmost care with the aim of helping students to ace their exams without fear. To get a better hold on the concepts covered in this chapter, students can access the ICSE Selina Solutions Class 8 Maths Chapter 21 Surface Area, Volume and Capacity free PDF, from the link which is given below.

This chapter has the concepts explained in a comprehensive manner to make learning fun for the students. It is highly recommended for the Class 8 students to solve the questions present in the textbook using the solutions for a better understanding of the concepts. It will also help the students with their analytical and logical thinking abilities, which is necessary to perform well in the annual exam.

Download ICSE Class 8 Maths Selina Solutions Chapter 21:-Download Here

icse class 8 maths may3 selina solutions chapter 21 surface area volume and capacity 01
icse class 8 maths may3 selina solutions chapter 21 surface area volume and capacity 02
icse class 8 maths may3 selina solutions chapter 21 surface area volume and capacity 03
icse class 8 maths may3 selina solutions chapter 21 surface area volume and capacity 04
icse class 8 maths may3 selina solutions chapter 21 surface area volume and capacity 05
icse class 8 maths may3 selina solutions chapter 21 surface area volume and capacity 06
icse class 8 maths may3 selina solutions chapter 21 surface area volume and capacity 07
icse class 8 maths may3 selina solutions chapter 21 surface area volume and capacity 08
icse class 8 maths may3 selina solutions chapter 21 surface area volume and capacity 09
icse class 8 maths may3 selina solutions chapter 21 surface area volume and capacity 10
icse class 8 maths may3 selina solutions chapter 21 surface area volume and capacity 11

Access Selina Solutions Concise Maths Class 8 Chapter 21: Surface Area, Volume and Capacity

Exercise

Question 1. 

Find the volume and the total surface area of a cuboid, whose:

(i) Length = 15cm, breadth = 10cm and height = 8cm.

Solution:-

We know that

ICSE Class 8 Maths Selina Solutions Chapter 21 Image 1

(ii) l = 3.5m, b = 2.6m and h = 90cm,

Solution:-

ICSE Class 8 Maths Selina Solutions Chapter 21 Image 2

Question 2.

ICSE Class 8 Maths Selina Solutions Chapter 21 Image 3

(ii) The volume of a cuboid is 7.68 m3. If its length = 3.2m and height =1.0m; find its breadth.

Solution:-

 Volume of a cuboid =7.68 m3

Length of a cuboid =3.2 m

Height of a cuboid =1.0 m

Here

Length x Breadth x Height = Volume of a cuboid

Substituting the values

3.2 × Breadth × 1.0=7.68

By further calculation

ICSE Class 8 Maths Selina Solutions Chapter 21 Image 4

(iii) The breadth and height of a rectangular solid are 1.20 m and 80 cm respectively. If the volume of the cuboid is 1.92 m3; find its length.

Solution:-

Volume of a rectangular solid =1.92 m3

Breadth of a rectangular solid = 1.20 m

Height of a rectangular solid =80 cm=0.8 m

Here

Length × Breadth × Height = Volume of a rectangular solid (cubical)

Substituting the values

Length × 1.20 × 0.8 = 1.92

By further calculation

Length × 0.96 = 1.92

ICSE Class 8 Maths Selina Solutions Chapter 21 Image 5

Question 3.

The length, breadth and height of a cuboid are in the ratio 5:3:2. If its volume is 240cm3, find its dimensions. (Dimensions means: its length, breadth and height). Also find the total surface area of the cuboid.

Solution:-

Consider length of the given cuboid =5x

Breadth of the given cuboid =3x

Height of the given cuboid =2x

We know that

Volume of the given cuboid = Length × Breadth ×height

Substituting the values

=5x×3x×2x=30x3

It is given that

Volume =240cm3

Substituting the values

30x3=240cm3

By further calculation

ICSE Class 8 Maths Selina Solutions Chapter 21 Image 6

Here

Length of the given cube =5x=5×2=10cm

Breadth of the given cube =3x=3×2=6cm

Height of the given cube =2x=2×2=4cm

We know that

Total surface area of the given cuboid =2(1×b+b×h+h×1)

Substituting the values

=2(10×6+6×4+4×10)=2(60+24+40)=2×124=248cm2

Question 4.

The length, breadth and height of a cuboid are in the ratio 6:5:3. If its total surface area is 504 c m2; find its dimensions. Also, find the volume of the cuboid.

Solution:-

Consider length of the cuboid =6x

Breadth of the cuboid =5x

Height of the cuboid =3x

We know that

Total surface area of the given cuboid =2(1×b+b×h+h×l)

Substituting the values

ICSE Class 8 Maths Selina Solutions Chapter 21 Image 7

x=2 cm

Here

Length of the cuboid =6x=6×2=12cm

Breadth of the cuboid =5x=5×2=10cm

Height of the cuboid =3x=3×2=6cm

We get

Volume of the cuboid =l×b×h=12×10×6=720cm3

Question 5.

Find the volume and total surface area of a cube whose edge is:

(i) 8 cm

Solution:-

Edge of the given cube =8cm

We know that

ICSE Class 8 Maths Selina Solutions Chapter 21 Image 8

(ii) 2m 40 cm.

Solution:-

(ii)Edge of the given cube =2 m 40 cm=2.40 m

We know that

ICSE Class 8 Maths Selina Solutions Chapter 21 Image 9

Question 6.

Find the length of each edge of a cube, if its volume is:

ICSE Class 8 Maths Selina Solutions Chapter 21 Image 10

ICSE Class 8 Maths Selina Solutions Chapter 21 Image 11

ICSE Class 8 Maths Selina Solutions Chapter 21 Image 12

Question 7.

The total surface area of a cube is 216 cm2. Find its volume.

Solution:-

ICSE Class 8 Maths Selina Solutions Chapter 21 Image 13

ICSE Class 8 Maths Selina Solutions Chapter 21 Image 14

Question 8.

A solid cuboid of metal has dimensions 24 cm, 18 cm and 4 cm. Find its volume.

Solution:-

It is given that

Length of the cuboid =24 cm

Breadth of the cuboid =18 cm

Height of the cuboid =4 cm

We know that

ICSE Class 8 Maths Selina Solutions Chapter 21 Image 15

Question 9. 

A wall 9 m long, 6 m high and 20 cm thick, is to be constructed using bricks of dimensions 30 cm, 15 cm and 10 cm. How many bricks will be required?

 Solution:

It is given that

Length of the wall =9m=9×100cm=900cm

Height of the wall =6m=6×100cm=600cm

Breadth of the wall =20 cm

We know that

ICSE Class 8 Maths Selina Solutions Chapter 21 Image 16

Question 10. 

A solid cube of edge 14 cm is melted down and recasted into smaller and equal cubes each of edge 2 cm; find the number of smaller cubes obtained.

Solution:-

We know that

Edge of the big solid cube = 14 cm

ICSE Class 8 Maths Selina Solutions Chapter 21 Image 17

Question 11.

A closed box is cuboid in shape with length =40cm, breadth =30cm and height =50cm. It is made of thin metal sheet. Find the cost of metal sheet required to make 20 such boxes, if 1 m2 of metal sheet costs Rs. 45.

Solution:-

It is given that

Length of closed box (1) =40cm

Breadth (b) =30cm

And height (h) =50cm

ICSE Class 8 Maths Selina Solutions Chapter 21 Image 18

We know that

Total surface area =2(l×b+b×h+h×l)

Substituting the values

ICSE Class 8 Maths Selina Solutions Chapter 21 Image 19

Question 12.

Four cubes, each of edge 9 cm, are joined as shown below:

ICSE Class 8 Maths Selina Solutions Chapter 21 Image 20

Write the dimensions of the resulting cuboid obtained. Also, find the total surface area and the volume of the resulting cuboid.

Solution:-

Edge of each cube =9cm

(i) We know that

Length of the cuboid formed by 4 cubes (1) =9×4=36cm

Breadth (b) =9cm and height (h) = 9cm

(ii) Total surface area of the cuboid = 2(lb + bh + hl)

Substituting the values

ICSE Class 8 Maths Selina Solutions Chapter 21 Image 21

Question 13.

How many persons can be accommodated in a big-hall of dimensions 40 m, 25m and 15m; assuming that each person requires 5m3 of air?

Solution:-

ICSE Class 8 Maths Selina Solutions Chapter 21 Image 22

Question 14.

The dimension of a class-room are; length = 15m, breadth =12m and height =7.5m. Find, how many children can be accommodated in this class-room; assuming 3.6 m3 of air is needed for each child.

Solution:-

It is given that

Length of the room =15m

Breadth of the room =12m

Height of the room =7.5m

We know that

ICSE Class 8 Maths Selina Solutions Chapter 21 Image 23

Question 15.

The length, breadth and height of a room are 6m, 5.4m and 4 m respectively. Find the area of:

(i) Its four-walls

(ii) Its roof.

Solution:-

It is given that

Length of the room = 6m

Breadth of the room = 5.4m

Height of the room = 4m

ICSE Class 8 Maths Selina Solutions Chapter 21 Image 24

Leave a Comment

Your Mobile number and Email id will not be published. Required fields are marked *

*

*

BOOK

Free Class