1.

A slant height of a furstom of a cone is 4cm and perimeter of its circular bases are 18cm and 6cm. find the curved surface area of a furstom of a cone​

Answer»

ANSWER:

  • Curved SURFACE area of a furstom of a cone is 48cm²

Given :

  • A slant HEIGHT of a furstom of a cone is 4cm
  • PERIMETER of its circular bases are 18cm and 6cm

To find :

  • Curved surface area of furstom of a cone

Solution :

As we know that,

  • Curved surface area of cone = π(r₁ + r₂) l

Where,

  • r₁ is 18cm
  • r₂ is 6cm
  • l is 4cm

Now , We need to find the r₁

Given,

  • Circumference of r₁ = 18cm

As we know that,

  • Circumference = 2πr

》2πr₁ = 18

》r₁ = 18/2 × 1/π

》r₁ = 9/π

Now we need to find r₂ :

Given,

  • Circumference of r₂ = 6cm

As we know that,

  • Circumference = 2πr

》2πr₂= 6

》r₂ = 6/2 × 1/π

》 r₂ = 3/π

Now we need to find the curved surface area of furstom of a cone :

  • Curved surface area of cone = π(r₁ + r₂) l

Where,

  • r₁ = 9/π
  • r₂ = 3/π
  • l = 4

》Curved surface area of cone = π(r₁ + r₂) l

》π × (9/π + 3/π) 4

》π × (9 + 3 / π) × 4

》π × 12/π × 4

》48cm²

Hence , Curved surface area of a furstom of a cone is 48cm²


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