Answer: √3 a²/4.
- A a²/2
- B √3 a²/4
- C a²√3
- D a²/4
Correct answer: B. √3 a²/4
Explanation: Area of equilateral triangle = (√3/4)a².
Three standard 3D solids and their key formulas: a cylinder's volume scales with the full height, a cone's volume is exactly one-third of the cylinder with the same base and height, and a sphere's volume and surface area both follow distinct r-based formulas worth memorising separately.
Concept context
Perimeters, areas, and volumes of 2D and 3D shapes