Questions & Answers

Question

Answers

A) Rs. 50

B) Rs. 75

C) Rs. 100

D) Rs. 200

Answer
Verified

We know that plastering cost depends on the surface area. In this case, only 4 walls of the room are plastering. So, we take the lateral surface area. Let it be S. It is given by,

${\text{S = 2h}}\left( {{\text{l + b}}} \right)$ where l is the length of the room, b is the breadth of the room and h is the height of the room.

Let the new surface area when length, breadth and height is doubled be S’. Then l becomes 2l, b becomes 2b and h becomes 2h. Its surface area is given by,

\[{{\text{S}}^{\text{'}}}{\text{ = 2} \times \text{2h}}\left( {{\text{2l + 2b}}} \right){\text{ = 4} \times \text{2h}}\left( {{\text{l + b}}} \right){\text{ = 4S}}\]

From the above equation, we can understand that the surface area has increased 4 times. So the cost will also increase 4 times.

As the given cost is Rs. 25, the new cost will be 4 times Rs. 25,

New cost${{ = 4 \times 25 = 100}}$

Therefore, the new cost is Rs.100