2022 · Q45
In triangle ABC, AB = 12 cm, BC = 9 cm and AC = 15 cm. What is the radius of the circumcircle of the triangle?
Elementary MathematicsCircles
- A4.5 cm
- B6 cm
- C7.5 cm
- D15 cm
Explanation
The 9–12–15 triangle is right-angled, so its hypotenuse is a diameter of the circumcircle (Thales' theorem); R = 15/2 = 7.5 cm. The distractor 15 cm confuses the diameter with the radius. The keyed option is C.