Question : The height and the total surface area of a right circular cylinder are 4 cm and 8$\pi$ sq cm, respectively. The radius of the base of the cylinder is:
Option 1: $\left ( 2\sqrt{2}-2 \right )\ \text{cm}$
Option 2: $\left ( 2-\sqrt{2}\right )\ \text{cm}$
Option 3: $2\ \text{cm}$
Option 4: $\sqrt{2}\ \text{cm}$
Latest: SSC CGL preparation tips to crack the exam
Don't Miss: SSC CGL complete guide
New: Unlock 10% OFF on PTE Academic. Use Code: 'C360SPL10'
Correct Answer: $\left ( 2\sqrt{2}-2 \right )\ \text{cm}$
Solution : Given: Height of the cylinder = 4 cm Total surface area = 8$\pi$ cm 2 ⇒ $2\pi r(h+r) = 8\pi$ ⇒ $r(4+r) = 4$ ⇒ $r^2+4r-4=0$ Using quadratic formula: $r= \frac{-b\pm \sqrt{b^2-4ac}}{2a}$ ⇒ $r= \frac{-4\pm \sqrt{4^2+4\times1\times4}}{2\times1}$ ⇒ $r= \frac{-4\pm \sqrt{16+16}}{2}$ ⇒ $r=\frac{-4\pm 4\sqrt{2}}{2}$ $\therefore r=(2\sqrt{2}-2)\ \text{cm}$ Hence, the correct answer is $(2\sqrt{2}-2)\ \text{cm}$.
Candidates can download this ebook to know all about SSC CGL.
Answer Key | Eligibility | Application | Selection Process | Preparation Tips | Result | Admit Card
Question : The volume of a solid right circular cylinder of height 8 cm is $392 \pi$ cm3. Its curved surface area (in cm2) is:
Question : The lateral surface area of a frustum of a right circular cone, if the area of its base is 16$\pi$ cm2, the diameter of the circular upper surface is 4 cm and the slant height is 6 cm, will be:
Question : The curved surface area of a right circular cylinder of height 56 cm is 1408 cm². Find the diameter of the base of the cylinder.
Question : A sphere has the same curved surface area as a cone, with a vertical height of 40 cm and a radius of 30 cm. The radius of the sphere is:
Question : The curved surface area of a right circular cone of a base radius of 21 cm is 594 sq. cm. What is the slant height of the cone?
Regular exam updates, QnA, Predictors, College Applications & E-books now on your Mobile