Question

An open cuboidal box has dimensions $20cm\times 10cm\times 5cm$. Find the cost of painting the box from outside if the painting cost is ₹ $2/c{m}^2$.

• A. ₹ $500$
• B. ₹ 600
• C. ₹ $1000$
• D. ₹ $2000$

Answer 1

The correct option is C

₹ $1000$

Since, the box is open, there are only five faces instead of six as shown in the figure:

So, there are four walls and one base.

Area of two walls with length, $20cm$ $=2\times (20\times 5)=200c{m}^2$

Area of two walls with length, $10cm$ $=2\times (10\times 5)=100c{m}^2$

Area of the base $=20\times 10=200c{m}^2$

Total surface area $=$ Area of four walls $+$ Area of base $=200+100+200=500c{m}^2$

Cost of painting is ₹ $2/c{m}^2$

So, total cost of painting the box from outside $=500\times 2=$ ₹ $1000$