2023 · Q66
A solid sphere of radius 3 cm is melted to form a hollow cylinder of height 4 cm and external diameter 10 cm. What is the thickness of the cylinder?
Elementary MathematicsMensuration
- A0.42 cm
- B0.46 cm
- C0.50 cm
- D1.00 cm
Explanation
The sphere's volume is (4/3)π·3³ = 36π cm³. The hollow cylinder of height 4 cm, external radius 5 cm and internal radius r has volume π(5² − r²)·4 = 36π, giving 25 − r² = 9, so r = 4 cm. The thickness is 5 − 4 = 1 cm. The answer is (D).