Question

A wooden box in the shape of a cube of volume 64 $c{m}^3$ is to be painted at a rate of ₹20/$c{m}^2$. Calculate the cost of painting.

• A. ₹1,920
• B. ₹1,820
• C. ₹960
• D. ₹480

Answer 1

The correct option is A ₹1,920

Let's consider the length of the side of the cubical box as $a$.
So, the volume = $a^3$
Now, according to the question
$a^3=64c{m}^3$
⇒ $a=4cm$
Area of cube to be painted is its total surface area.
Now, we know that the total surface area of a cube = $6a^2$
So, the total surface area of the given wooden box = $6\times (4\times 4)$
= $96c{m}^2$
Cost of painting = Rate × Total surface area
= ₹20/$c{m}^2$ × $96c{m}^2$
= ₹1,920