Question

Find the cost of painting the four walls of a
room at the rate of Rs per square metre, if its
perimeter is 100 m and height 9 m.​

Answer 1

Answer:

Rs 8100,    if rate is 9.  else, substitute the value of rate in the last eqⁿ

Step-by-step explanation:

Perimeter of rectangle = 2(l + b)

                               100 = 2(l + b)

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

                              = 100*9

                              = 900

Cost of painting = rate x area

                           = Rs 9 x 900

                           = Rs 8100

Answer 2

Given :-

Perimeter = 100 m

Height = 9 m

To Find :-

Cost of painting at Rs 5 per m

Solution :-

It is given that perimeter is 100 m,

We know that

Area of 4 walls = 2(l +b)h

Perimeter = 100

So,

We will write 2(l + b) as 100

So,

$\sf Area \; of \; 4\;walls= 100 \times9$

$\sf Area = 900 m^2$

Now,

$\sf Cost = 5 \times 900$

$\sf Cost = 4500$

Note -

At last you haven't mentioned the rate. So, I have taken rate as 5 per m