CBSE 8th Mensuration Solved Questions

11. A flooring tile has a shape of a parallelogram whose base is 28cm and the corresponding height is 20cm . how many such tiles are required to cover a floor of a area 2800cm²

Solution: Area of each parallelogram tile

= Base of the parallelogram × corresponding height of the parallelogram

= 28 cm × 20 cm= 560 cm²

Area of the floor = 28 m² = 2800 × (100 cm)² = 2800 × 10000 cm²

Number of tiles × Area of each parallelogram tile = Area of the floor

Number of tiles = Area of the floor/ Area of each parallelogram tile

                            = 2800 × 10000 cm²  /560 cm²   = 50000 tiles

12. The rainfall recorded on a certain day was  5cm. Find the volume of water that fell on 2 hectare field.

Solution: The volume of water= Area of ground x h= 2 hectare x 5cm = 2x10000m² x 5/100m=1000m³ = 1000x1000Lit=1000000Lit.{1m3=1000L}

13. Rain water which falls on a flat rectangular surface of length 6 m and breadth 4 m is transferred into a cylindrical vessel of internal radius 20 cm. What will be the height of water in the cylindrical vessel if the rain fall is 1 cm  (Take π = 3.14)

Solution : Let the height of the water level in the cylindrical vessel be h cm

Volume of the rain water = 600 × 400 × 1 cm³

Volume of water in the cylindrical vessel = π (20)2 × h cm³

A/Q,   600 × 400 × 1 = π (20)2 × h  or h =600/3.14 cm = 191 cm

14. The areas of three adjacent faces of a cuboid are 180 cm sq., 96 cm sq. and 120cm sq. what the volume of cuboid is. Please give me the answer

Solution:  lx b = 180       b x h = 96        h x l =120

l x b x b x h x h x  l = 180 x 96 x 120

(lbh)²= 180 x 96 x120

l b h = √(180 x 96 x120 ) =2073600

Volume   = √2073600   = 1440 cm³

15.  If a solid cylinder has a total surface area 462 sq. cm. & CSA  is 1/3rd of it so what is the volume of the cylinder?

Solution : Let the radius and height of the cylinder be r cm and h cm respectively.

Given, Total surface area of the cylinder = 462 cm²

∴ 2p r (r + h) = 462 cm²       .. .(1)

Lateral surface area of cylinder =  1/3 × Total surface area of cylinder (Given)

∴ 2prh =1/3 × 462 = 154 cm² ... (2)

From (1) and (2), we have

{2pr(r+h}/{2pr} = 462 cm²       / 154 cm²

(r+h) / h = 3

r = 3h-h=2h

r = 2h

From (2), we have

2prh =154 cm²

(2 x22rxr) /(7x2)}

r = 7cm

h = r/2=7/2=3.5cm

∴ Volume of the cylinder  = pr²h =22x7x7/3.5=539 cm²

 CBSE ADDA: 8th Mensuration Solved Questions: {For question 1 to 10 }