The curved surface area of a cylindrical pillar is 264 m2 and its volume is 924 m3. Find the ratio of its diameter to its height.
Aptitude
Volume and Surface Area
Difficulty: Medium
Choose an option
-
A7 : 3
-
B3 : 7
-
C2 : 1
-
D5 : 3
Answer
Correct Answer: 7 : 3
Explanation
Problem Restatement
For a cylinder, use CSA = 2πrh and Volume = πr^2h to determine the ratio diameter : height.
Given formulas
- Curved surface area: 2πr h = 264
- Volume: πr^2 h = 924
Concept / Approach
Eliminate h or r using the two equations to find dimensions up to a constant and then form the ratio.
Step-by-step calculation
From volume: πr^2h = 924 → h = 924 ÷ (πr^2)Substitute in CSA: 2πr × [924 ÷ (πr^2)] = 264Simplify: 2 × 924 ÷ r = 264 → 1848 ÷ r = 264 → r = 1848 ÷ 264 = 7Radius r = 7 m → Diameter d = 14 mFind height: πr^2h = 924 → π(49)h = 924 → h = 924 ÷ (49π) ≈ 6Therefore, diameter : height = 14 : 6 = 7 : 3
Check
- CSA = 2πr h = 2&pi(7)(6) = 84π ≈ 264 ✓
Final Answer
Ratio (diameter : height) = 7 : 3.