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A cone has a slant height of 7.5cm and a radius of 4.5 cm. What is the volume of the cone?

Sagot :

  • h²=7.5²-4.5²
  • h²=6²
  • h=6cm

Now

volume:-

  • 1/3πr²h
  • 1/3π(4.5)²(6)
  • π(20.25)(2)
  • 40.5πcm³

Answer:

  • Volume of cone = 127.17 cm³

Step-by-step explanation:

In the question we are given ,

  • Slant height = 7.5 cm

  • Radius = 4.5 cm

And we are asked to find the volume of cone. We know that ,

[tex] \red{\boxed{ \rm{Volume \: of \: cone = \frac{1}{3} \pi r {}^{2}h }}}[/tex]

Where ,

  • π = 3.14

  • r = 4.5 cm

  • h = Not given

So , for finding volume of cone we must have to find the height of cone using slant height formula i.e. ,

[tex] \green{\boxed{ \sf{l {}^{2} = h {}^{2} + r {}^{2} }}}[/tex]

Where ,

  • l = slant height

  • h = height

  • r = radius

Now , substituting values :

[tex] \hookrightarrow \: 7.5 {}^{2} = h {}^{2} + 4.5 {}^{2} [/tex]

Transposing 4.5 to left hand side :

[tex] \hookrightarrow \: 7.5 {}^{2} - 4.5 {}^{2} = h {}^{2} [/tex]

[tex] \hookrightarrow \:56.25 - 20.25 = h {}^{2} [/tex]

On further calculations we get :

[tex] \hookrightarrow \:h {}^{2} = 36[/tex]

[tex] \hookrightarrow \:h = \sqrt{36} [/tex]

We know that 6 × 6 is equal to 36 that means square root of 36 is 6 . So :

[tex] \hookrightarrow \pink{\boxed{\bold{h = 6 \: cm}}}[/tex]

  • Therefore, height of cylinder is 6 cm .

Now finding volume :

Substituting values in volume formula :

[tex] \longrightarrow\: \frac{1}{ \cancel{3} } \times 3.14 \times (4.5) {}^{2} \times \cancel{6}[/tex]

Step 1 : By cancelling 6 with 3 we get :

[tex] \longrightarrow \: 3.14 \times 20.25 \times 2[/tex]

Step 2 : Multiplying 20.25 with 2 :

[tex] \longrightarrow \:3.14 \times 40.50[/tex]

Step 3 : Multiplying 3.14 with 40.50 :

[tex] \longrightarrow \: \purple{\boxed{\bold{127.17 \: cm {}^{3} }}}[/tex]

  • Therefore, volume of cone is 127.17 cm³ .

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