Question

A closed box made of steel of uniform thickness has length, breadth and height $12$ dm, $10$ dm and $8$ dm respectively. If the thickness of the steel sheet is $1$ dm, then the inner surface area is

• A. $456$ dm${}^2$
• B. $376$ dm${}^2$
• C. $264$ dm${}^2$
• D. $696$ dm${}^2$

Answer 1

Answer: (B)

$376$ dm${}^2$

The outer length, breadth, height of the box are $12,10,8$ dm with a thickness of $1$dm
$\therefore$ inner length, breadth and height will be $10,8,6$ dm respectively.
Area of inner surface $=2(lb+bh+hl)$
$=2(10\times 8+8\times 6+6\times 10)$
$=376$ dm${}^2$