Question

The length of the longest diagonal of a cuboid of dimensions 3 cm × 4 cm × 12 cm is

• A. 12 cm
• B. 13 cm
• C. 8 cm
• D. $4\sqrt{10}cm$

Answer 1

The correct option is B 13 cm

Given that the dimensions of the cuboid are 3 cm, 4 cm and 12 cm.
Let, length (l) = 3 cm, breadth (b) = 4cm and height (h) = 12cm
$\therefore \text{Length of longest diagonal}=\sqrt{l^2+b^2+h^2}$
$=\sqrt{3^2+4^2+{12}^2}$
$=\sqrt{9+16+144}$
$=\sqrt{169}$
= 13 cm
Therefore, the length of the longest diagonal of the cuboid is 13 cm.
Hence, the correct answer is option (b).