The area of base of a cylinder is 25$\pi$ cm$^2$. If the height of cylinder is 9 cm, then find the total surface area of cylinder.

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RRB NTPC Exam 27 Jan 2021 click here to view all questions

The area of base of a cylinder is 25$\pi$ cm$^2$. If the height of cylinder is 9 cm, then find the total surface area of cylinder.

A$$440 \, \text{cm}^2$$

B$$240 \, \text{cm}^2$$

C$$420 \, \text{cm}^2$$

D$$220 \, \text{cm}^2$$

Akhilesh ? Apr 3 '25 at 19:31

correct answer is: 440 cm²
Explanation: The total surface area of a cylinder is calculated using the formula:

\[ \text{TSA} = 2\pi r^2 + 2\pi r h \]

Given the area of the base \( \pi r^2 = 25\pi \, \text{cm}^2 \), we find \( r = 5 \, \text{cm} \)

With height \( h = 9 \, \text{cm} \), the total surface area is:

\(\text{TSA} = 2\pi (5)^2 + 2\pi (5)(9) \)

\(TSA= 50\pi + 90\pi \)

\(TSA= 140\pi \, \text{cm}^2\)

\(TSA = \approx 440 \, \text{cm}^2\)

Thus, the correct answer is OPTION a.

• OPTION a: Correct, as shown by the calculation.
• OPTION b: Incorrect, too low.
• OPTION c: Incorrect, too high.
• OPTION d: Incorrect, too low.

All DiscussionsClick here to write answer

correct answer is: 440 cm² Explanation: The total surface area of a cylinder is calculated using the formula: \[ \text{TSA} = 2\pi r^2 + 2\pi r h \] Given the area of the base \( \pi r^2 = 25\pi \, \text{cm}^2 \), we find \( r = 5 \, \text{cm} \) With height \( h = 9 \, \text{cm} \), the total surface area is: \(\text{TSA} = 2\pi (5)^2 + 2\pi (5)(9) \) \(TSA= 50\pi + 90\pi \) \(TSA= 140\pi \, \text{cm}^2\) \(TSA = \approx 440 \, \text{cm}^2\) Thus, the correct answer is OPTION a. OPTION a: Correct, as shown by the calculation. OPTION b: Incorrect, too low. OPTION c: Incorrect, too high. OPTION d: Incorrect, too low. Akhilesh ? answered Apr 3 '25 at 19:31

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