**Question:**

A box with a lid is made of wood which is 3 cm thick. Its external length, breadth and height are 56 cm, 39 cm and 30 cm respectively. Find the capacity of the box. Also find the volume of wood used to make the box.

**Solution:**

External length $=56 \mathrm{~cm}$

External width $=39 \mathrm{~cm}$

External height $=30 \mathrm{~cm}$

External volume of the box $=56 \times 39 \times 30=65520 \mathrm{~cm}^{3}$

Thickness of wood $=3 \mathrm{~cm}$

$\therefore$ Internal length $=56-(3 \times 2)=50 \mathrm{~cm}$

Internal width $=39-(3 \times 2)=33 \mathrm{~cm}$

Internal height $=30-(3 \times 2)=24 \mathrm{~cm}$

Capacity of the box $=$ Internal volume of the box $=50 \times 33 \times 24=39600 \mathrm{~cm}^{3}$

Volume of wood $=$ External volume $-$ Internal volume $=65520-39600=25920 \mathrm{~cm}^{3}$