Daniel is painting the walls and ceiling of a cuboidal hall with length, breadth and height of 15 m, 10 m and 7 m respectively. From each can of paint 100 m 2 of area is painted. How many cans of paint will she need to paint the room?

NCERT - Mathematics

Book: NCERT - Mathematics

Chapter: 11. Mensuration

Subject: Maths - Class 8^th

Q. No. 5 of Exercises 11.3

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5

Daniel is painting the walls and ceiling of a cuboidal hall with length, breadth and height of 15 m, 10 m and 7 m respectively. From each can of paint 100 m² of area is painted. How many cans of paint will she need to paint the room?

Area of Walls of a Room = 2 x h x (l + b)

= 2 x 7 x (15 + 10)

= 350 m²

Area of Roof = Area of Floor = 150 m²

Total Area to be painted = 350 + 150 = 500 m²

As, one can of paint is enough for 100 sq m

So, 500/100 = 5 cans are needed to paint the hall.

6

Chapter Exercises

Exercises 11.1

Exercises 11.2

Exercises 11.3

Exercises 11.4

1

There are two cuboidal boxes as shown in the adjoining figure. Which box requires the lesser amount of material to make?

2

A suitcase with measures 80 cm × 48 cm × 24 cm is to be covered with a tarpaulin cloth. How many metres of tarpaulin of width 96 cm is required to cover 100 such suitcases?

3

Find the side of a cube whose surface area is 600 cm².

4

Rukhsar painted the outside of the cabinet of measure 1 m × 2 m × 1.5 m. How much surface area did she cover if she painted all except the bottom of the cabinet.

5

Daniel is painting the walls and ceiling of a cuboidal hall with length, breadth and height of 15 m, 10 m and 7 m respectively. From each can of paint 100 m² of area is painted. How many cans of paint will she need to paint the room?

6

Describe how the two figures at the right are alike and how they are different. Which box has larger lateral surface area?

7

A closed cylindrical tank of radius 7 m and height 3 m is made from a sheet of metal. How much sheet of metal is required?

8

The lateral surface area of a hollow cylinder is 4224 cm². It is cut along its height and formed a rectangular sheet of width 33 cm. Find the perimeter of rectangular sheet?

9

A road roller takes 750 complete revolutions to move once over to level a road. Find the area of the road if the diameter of a road roller is 84 cm and length is 1 m.

10

A company packages its milk powder in cylindrical container whose base has a diameter of 14 cm and height 20 cm. Company places a label around the surface of the container (as shown in the figure). If the label is placed 2 cm from top and bottom, what is the area of the label.