Question

1. The perimeter of floor of rectangular hall is 250m. The cost of the white washing its four walls
is 15000. The height of the room is
5 m
4 m
6m
8 m​

Answer 1

Perimeter of the floor of hall = 250 m.

Cost of painting the four walls = Rs.15,000

Let the dimension of rectangular hall be l\times b\times hl×b×h m.

Area of four walls is given by,

A= 2lh + 2bhAA=2lh+2bhA

A=2(l + b) hA=2(l+b)h ....(1)

Perimeter of the floor of hall is given by,

P= 2(l + b)P=2(l+b)

We have given P=250 m

250= 2(l + b)250=2(l+b) ....(2)

Substitute (2) in (1),

A=250\times hA=250×h

A=250h\ m^2A=250h m

2

Cost of painting per m² area = Rs.10

Cost of painting 250h\ m^2250h m

2

area = Rs.250h\times 10Rs.250h×10

Cost of painting 250h\ m^2250h m

2

area = Rs.2500h

The cost of painting the walls is Rs.15000 .

i.e. 2500h=150002500h=15000

h=\frac{15000}{2500}h=

2500

15000

h=6h=6

Therefore, the height of the hall is 6 m.