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A solid cone of height 8 cm and base radius 6 cm is melted and recast into identical cones, each of height 2 cm and diameter 1 cm. Find the number of cones formed.

Mensuration

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Answer

For larger cone,

Height (h1) = 8 cm

Radius (r1) = 6 cm

For smaller cones,

Height (h2) = 2 cm

Radius (r2) = 12\dfrac{1}{2} = 0.5 cm

Let no. of smaller cones be n.

Volume of larger cone = n × Volume of smaller cones

13πr12h1=n×13πr22h2r12h1=n×r22h2n=r12h1r22h2n=62×8(0.5)2×2n=2880.5n=576.\Rightarrow \dfrac{1}{3}πr1^2h1 = n \times \dfrac{1}{3}πr2^2h2 \\[1em] \Rightarrow r1^2h1 = n \times r2^2h2 \\[1em] \Rightarrow n = \dfrac{r1^2h1}{r2^2h2} \\[1em] \Rightarrow n = \dfrac{6^2 \times 8}{(0.5)^2 \times 2} \\[1em] \Rightarrow n = \dfrac{288}{0.5} \\[1em] \Rightarrow n = 576.

Hence, no. of cones formed = 576.

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