Question

"Question 3 The floor of a rectangular hall has a perimeter 250 m. If the cost of panting the four walls at the rate of Rs.10 per m^2 is Rs.15000, find the height of the hall. [Hint: Area of the four walls = Lateral surface area.]

Class 9 - Math - Surface Areas and Volumes Page 213"

Answer 1

Perimeter of rectangular hall = 2(l + b) = 250 m
Total cost of painting = Rs.15000
Rate per m2 = Rs.10
Area of four walls = 2(l + b) h m2 = (250×h) m2
A/q,
(250×h)×10 = Rs.15000
⇒ 2500×h = Rs.15000 
⇒ h = 15000/2500 m
⇒ h = 6 m 
Thus the height of the hall is 6 m.

Answer 2

Given:

Perimeter of the rectangular hall = 250m

Cost of painting 4 walls = Rs. 10/m² is Rs.15000

To Find:

height of the hall.

Solution:

Lateral surface area = 2× height(length + wide)

Perimeter of the hall = 2(length+ width)

Length + Width = 125

Cost of painting the lateral surface area = 15000/10

                                                                   = 1500m²

Now,

Height of the hall = 15000/250

                              = 6m.

Therefore, the height of the hall = 6m