A right triangle with sides 3 cm, 4 cm and 5 cm is rotated the side of 3 cm to form a cone. The volume of the cone so formed is:

A. 12$$\pi$$ cm3

B. 15$$\pi$$ cm3

C. 16$$\pi$$ cm3

D. 20$$\pi$$ cm3

Answer: Option A

Solution(By Examveda Team)

Volume and Surface Area mcq solution image
$$\eqalign{ & {\text{Clearly}}, \cr & {\text{We have }}r = 3\,{\text{cm}}\,{\text{and}}\,h = 4\,{\text{cm}} \cr & \therefore \,\,\,{\text{Volume}} \cr & = \frac{1}{3}\pi {r^2}h \cr & = \left( {\frac{1}{3} \times \pi \times {3^2} \times 4} \right){\text{c}}{{\text{m}}^3} \cr & = 12\pi \,{\text{c}}{{\text{m}}^3} \cr} $$

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Comments ( 2 )

  1. Noumaan Malik
    Noumaan Malik :
    3 years ago

    They have said that to rotate around 3 cm side.
    That means to make a cone we have to make a round circle around 3 cm line.

  2. Seema
    Seema :
    5 years ago

    How do we know that 3 will be base & 4 will be height. It can be vice versa leading to 16pie.
    Pls suggest

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