Question

The outer length, breadth and height of a wooden box open at the top are $10$ cm, $8$ cm and $5$ cm respectively. If the thickness of the wood is $1$ cm, the total surface area of the box is

• A. $420c{m}^2$
• B. $452c{m}^2$
• C. $451c{m}^2$
• D. $483c{m}^2$

Answer 1

The correct option is A $420c{m}^2$

Inner dimensions are $10-2$, $8-2$ and $5-1$
i. e., $8$ cm, $6$ cm. and $4$ cm.
$\therefore$ Outer surface $=10\times 8+2\times 5(10+8)=80+180=260c{m}^2$
and inner surface $=8\times 6+2\times 4(8+6)=48+112=160c{m}^2$
$\therefore$ Total surface area of the box $=260+160=420c{m}^2$