2022 · Q80
The diameter of a sphere made of copper is 3 cm. The sphere is melted and recast into a wire. If the length of the wire is half metre, then what is the diameter of the wire?
Elementary MathematicsMensuration
- A0.3 cm
- B0.45 cm
- C0.6 cm
- D0.75 cm
Explanation
Sphere volume = (4/3)π(1.5)³ = 4.5π = π(d/2)²·50, so d² = 0.36 and d = 0.6 cm. Halving the diameter instead of taking the square root of the area ratio is the common error. The keyed option is C.