Question:
What is the maximum length of a pencil that can be placed in a rectangular box of dimensions (8 cm × 6 cm × 5 cm)?
(a) 8 cm
(b) 9.5 cm
(c) 19 cm
(d) 11.2 cm
Solution:
(d) 11.2 cm
Maximum length of the pencil = diagonal of the box
$=\sqrt{l^{2}+b^{2}+h^{2}}$
$=\sqrt{8^{2}+6^{2}+5^{2}} \mathrm{~cm}$
$=\sqrt{64+36+25} \mathrm{~cm}$
$=\sqrt{125} \mathrm{~cm}$
$=11.2 \mathrm{~cm}$