Question

plastic drum of cylindrical shape is made by melting spherical solid plastic balls of radius 1 cm find the number of spherical balls required to make the drum of thickness 2 cm and height 90 cm and Outer radius 30 cm drum has no lid

Answer 1

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Answer 2

7830 Plastic balls would be required to make the drum

1)  The volume of the drum would be volume of outer cylinder - volume of inner cylinder.

2) Outer radius = 30 cm, Inner radius = 30-2 = 28 cm.

3) Volume of the drum  = π(30)²*90 - π(28)²*90 = π*90*116 = 10440π cm³

4) Volume of one plastic ball =4 πr³/3 = 4π/3 *(1)³ = 4π/3 cm³

5) Volume of n plastic balls = 4πn/3 cm³

6) Number of balls = 10440π/(4π/3) = 7830