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The surface area of a solid metallic sphere is 616 cm2. It is melted and recast into a cone of height 28 cm. Find the diameter of the base of the cone so formed - Mathematics

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प्रश्न

The surface area of a solid metallic sphere is 616 cm2. It is melted and recast into a cone of height 28 cm. Find the diameter of the base of the cone so formed (Use it =`22/7`)

संक्षेप में उत्तर

उत्तर

Given height of cone (h) = 28 cm

Given surface area of Sphere = 616cm2

We know surface area of sphere = 4πr2

⇒ 4πr2 = 616

⇒ `r^2=(616xx7)/(4xx22)`

⇒ r2 = 49

⇒ r = 7cm

∴ Radius of sphere(r) = 7cm

Let r1 be radius of cone

Given volume of cone = Volume of sphere

Volume of cone = `1/3pi(r^2)h`

`V_1=1/3pi(r_1)^2xx28cm^3`    ...........(1)

Volume of sphere `=(V_2)=4/3pir^3`

`V_2=4/3pi(7)^3cm^3`   .........(2)

(1) = (2) ⇒ V1 = V2

⇒ `1/3pi(r_1)^2xx28=4/3pi(7)^3`

⇒ `r_1^2 = 49`

r1 = 7cm

Radius of cone (r1) = 7cm

Diameter of base of cone (d1) = 2x7 = 14cm

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अध्याय 14: Surface Areas and Volumes - Exercise 14.1 [पृष्ठ २८]

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आरडी शर्मा Mathematics [English] Class 10
अध्याय 14 Surface Areas and Volumes
Exercise 14.1 | Q 20 | पृष्ठ २८

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