WAEC 2021 · Paper 1 · Q24

The diagonals of a rhombus are $12\text{ cm}$ and $5\text{ cm}$ . Calculate its perimeter.

Worked solution (try it first)

The diagonals of a rhombus bisect each other at right angles, so each side is the hypotenuse of a right-angled triangle with legs 6 cm and 2.5 cm.
By Pythagoras, the side is $\sqrt{6^2 + 2.5^2} = \sqrt{42.25} = 6.5$ cm.
The perimeter is $4 \times 6.5 = 26$ cm, option A.