Question

17. The dimensions of a room are 14 m x 10 m x 6.5 m. There are two door
and 4 windows in the room. Each door measures 2.5 mx1.2 m and
each window measures 1.5 mx1 m. Find the cost of painting the four
walls of the room at 35 per m.
​

Answer 1

Length of room = 14 m

Breadth of room = 10 m

Height of room = 6.5 m

Curved surface area of cuboid (room) = 2h(l + b)

Substitute the known values in above formula

→ 2 × 6.5 (14 + 10)

→ 13 (24)

→ 312 m²

Now,

Length of door = 2.5 m

Breadth of door = 1.2 m

Area of both door = 2(l × b)

→ 2(2.5 × 1.2)

→ 2(3)

→ 6 m²

Also,

Length of window = 1.5 m

Breadth of window = 1 m

Area of four windows = 4(l × b)

→ 4(1.5 × 1)

→ 4(1.5)

→ 6 m²

Area of wall without doors and windows = CSA of room - (Area of 2 doors + Area of 4 windows)

→ 312 - (6 + 6)

→ 312 - 12

→ 300 m²

Cost of painting the four walls of the room at 35 per m = 300 × 35

→ Rs. 10,500

Answer 2

Lenght=14m

Breadht=10m

Height=6.5m

Area of four walls of room= 2h(l+b)

=2×6.5(14+10)

=13×14

=182msq.

Now, Area of two doors = 2(l×b)

=2(2.5×1.2)

=2×3

=6msq.

Area of four windows= 4(l+b)

=4(1.5×1)

=4×1.5

=6msq.

Area of room excluding doors and windows= 182-(6+6)

= 160msq.

Cost of painting the four walls=

160×35=₹5600

ANSWER