Question

A wooden box (including the lid) has external dimensions $40cm\times 34cm\times 30cm$. If the wood is 1 cm thick, how many $c{m}^3$ of wood is used in it?

Answer 1

External dimensions of wooden box are $40cm\times 34cm\times 30cm$

Since, the wood is 1 cm thick, it means the internal dimensions will be
$(40-2)cm\times (34-2)cm\times (30-2)cm=38cm\times 32cm\times 28cm$
$\therefore$ Wood used for the box
= Volume of the wooden box with external dimensions - Volume of the wooden box with internal dimensions.
$=40\times 34\times 30-38\times 32\times 28=40800-34048=6752c{m}^3$