18. Area of a right-angled triangle is 30 cm². If its smallest side is 5 cm, then its hypotenuse is
(a) 14 cm
(b) 13 cm
(c) 12 cm
(d) 11 cm
Let smaller side = 5 cm, other side = x.
Area = \( \tfrac{1}{2} \times 5 \times x = 30 \implies x = 12 \).
Hypotenuse = \( \sqrt{5^2 + 12^2} = \sqrt{25 + 144} = \sqrt{169} = 13 \, cm \).