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Question -

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



Answer -

Given,

The height of the cone= 28 cm

Surface area of thesolid metallic sphere = 616 cm3

We know that,

Surface area of thesphere = 4πr2

So, 4πr2 =616

r2 =49

r = 7

Radius of the solidmetallic sphere = 7 cm

Let’s assume r to bethe radius of the cone

We know that,

Volume of the cone =1/3 πr2h

= 1/3 πr(28)….. (i)

Volume of the sphere =4/3 πr3

= 4/3 π73  ………. (ii)

On equating equations(i) and (ii), we have

1/3 πr(28)= 4/3 π73

Eliminating the commonterms, we get

r(28)= 4 x 73

r=49

r =7

So, diameter of thecone = 7 x 2 = 14 cm

Therefore, thediameter of the base of the cone is 14 cm

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