Cylinder – curved surface area from radius and height: Find the curved (lateral) surface area of a right circular cylinder with radius 7 cm and height 160 cm. Give the answer in cm^2.

Difficulty: Easy

Correct Answer: 7040 sq cm

Explanation:


Introduction / Context:
The curved surface area (CSA) of a cylinder equals the area of a rectangle with height h and width equal to the circumference 2πr. This is a direct substitution exercise once r and h are identified correctly.



Given Data / Assumptions:

  • r = 7 cm
  • h = 160 cm
  • CSA = 2πrh


Concept / Approach:
Compute 2 * π * 7 * 160 and evaluate numerically, preferably with π = 22/7 to get an exact integer in this setup (common in aptitude problems).



Step-by-Step Solution:
CSA = 2πrh = 2 * π * 7 * 160 = 2240π cm^2With π = 22/7 → CSA = 2240 * (22/7) = 320 * 22 = 7040 cm^2



Verification / Alternative check:
Using π ≈ 3.14 yields 2240 * 3.14 ≈ 7033.6 cm^2, which rounds to 7034–7040; consistent with the exact 22/7 value.



Why Other Options Are Wrong:
6020 and 5052 are too small; 7045 and 7080 overshoot the precise value; 7040 cm^2 matches the exact arithmetic with π = 22/7.



Common Pitfalls:
Using diameter instead of radius; confusing TSA with CSA; arithmetic errors multiplying large factors.



Final Answer:
7040 sq cm

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