Question

A wooden box (open at the top) of thickness 0.5 cm, length 21 cm, width 11 cm and height 6 cm
is painted on the inside. The expenses of painting are Rs. 70. What is the rate of painting per square
centimetres?
a. Re 0.7
b. Re 0.5
c. Re 0.1
d. Re 0.2

Answer 1

0.132 rs will be the exact answer to this question

Answer 2

Answer:

Had the thickness not been given, this would be an easy question to do.

But, since thickness is given, so we need to adjust the dimensions according to that thickness.

So, inside surface area becomes

Base area + area of 4 walls of the inside box.

Here the length reduces by 0.5 cm on both sides, therefore effective length becomes 20 cm.

Similarly, width also becomes 10 cm and height reduces just from bottom, that is one side, so height becomes 5.5 cm.

that is, (20 * 10) + 2 ( 20 +10 ) * 5.5

= 200 + 60 * 5.5

= 200 + 330

= 530 cm²

Now, this 530 cm² costs Rs 70

So 1 m² costs 70/ 530

= 0.13

Therefore, the rate of painting per cm² is Rs 0.1, that is option (c).