Question

The length, breadth and height of a room are X, Y and Z feet respectively. The cost of whitewashing the four walls of this room is Rs.2500. Find the cost of preparing another room whose length, breadth and height are double that of the previous room.

• A. 5000
• B. 12,500
• C. 10,000
• D. 20,000

Answer 1

The correct option is C 10,000

Surface area of the walls of the first room = 2(XZ + YZ)
Surface area of the walls of the second room
= 2(4XZ + 4YZ) = 8(XZ + YZ) = 4[2(XZ + YZ)] = 4 times the first area
$\Rightarrow$ Cost required = 4 $\times$ 2500 = Rs 10,000