A wooden box  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?
Inside dimensions of cube are as follows:
Length = $$21 - 2*(0.5) = 20$$
Width = $$11 - 2*(0.5) = 10$$
Height = $$6 - 0.5 = 5.5$$ (As top surface is open)
So total area painted = $$2(20 \times 5.5) + 2(10 \times 5.5) + (10 \times 20)$$
$$= 220 + 110 + 200$$
$$= 530$$ sq. cm.
Cost of painting 530 sq. cm. is 70
So cost per sq. cm. = $$\frac{70}{530} = 0.1$$ (nearly)
Create a FREE account and get: