Selina Concise Class 8 Math Chapter 21 Surface Area Volume and Capacity Exercise 21A Solution
Concise Mathematics – Class 8 Selina Exercise 21A Solution by experts | 10C Selina Concise Solution Class 8 | Class 8 Selina Concise Ex 21A Page 238 Solution | RK Bansal Class 8 ICSE Book Solution Online.
(1) Find the volume and the total surface area of a cuboid, whose:
(i) length = 15 cm, breadth = 10 cm and height = 8 cm
(ii) l = 3.5 m, b = 2.6 m and h = 90 cm.
Solution:
(2) (i) The volume of a cuboid is 3456 cm3 If its length = 24 cm and breadth = 18 cm, find its height.
(ii) The volume of a cuboid is 7.6 m3. If its length = 3.2 m and height = 1.0 m, find its breadth.
(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:
(3) The length, the breadth and the height of a cuboid are in the ratio 5:3:2. If its volume is 240 cm3, find its dimensions. Also, find the total surface area of the cuboid.
Solution:
(4) The length, breadth and height of a cuboid are in the ratio 6:5:3. If its total surface area is 504 cm2. find its dimensions. Also, find the volume of the cuboid.
Solution:
(5) Find the volume and total surface area of a cube whose each edge is:
(i) 8 cm (ii) 2 m 40 cm.
(6) Find the length of each edge of a cube, if its volume is:
(i) 8 cm (ii) 2 m 40 cm.
(7) The total surface area of a cube is 216 cm2. Find its volume.
Solution:
(8) A solid cuboid metal has dimensions 24 cm, 18 cm and 4 cm. Find its volume.
Solution:
Length of the cuboid = 24 cm
Breadth of the cuboid = 18 cm
Height of the cuboid = 4 cm
Volume of the cuboid = (24 x 18 x 4) cm3
= 1728
(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?
(10) A solid cube of edge 14 cm is melted down and recast into smaller and equal cubes each of edge 2 cm. Find the number of smaller cubes obtained.
Solution:
(11) A closed box is a cuboid in shape with length = 40 cm, breadth = 30 cm and height = 50 cm. Iy is made of thin metal sheet. Find the cost of metal sheets required to make 20 such boxes, if 1 m2 of metal sheet costs Rs. 45.
(12) Four cubes, each of edge 9 cm, are joined as shown below:
Write the dimensions of the cuboid obtained. Also, find total surface area and volume.
Solution: