Question

A house is in the shape of a cubical of length 20m, breadth 10m and height 5m. It has an opening of 2m $\times$ 2m on one of the walls for ventilation. Find the cost of cementing the walls of the house at Rs. 5 per $m^2$ .

• A. Rs. 1500
• B. Rs. 1480
• C. Rs. 1400
• D. Rs. 1450

Answer 1

The correct option is B

Rs. 1480

Lateral surface area = 2h(l + b)

l=20m, b=10m, h=5m.

Lateral surface area = 2 x 5 (20 + 10) = 300 $m^2$

Now, there is a ventilation on the wall.

So, Area of the ventilation = 2$\times$2

= $4m^2$

So, The area that needs to be cemented = Lateral surface area – Area of ventilation

= $300-4=296m^2$

Hence Cost of cementing =$296\times 5$

= Rs. 1480