Three solid metallic balls of radii 3 cm, 4 cm and 5 cm

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Three solid metallic balls of radii 3 cm, 4 cm and 5 cm are melted and moulded into a single solid ball. The radius of the new ball is :

1. 2 cm
2. 3 cm
3. 4 cm
4. 6 cm

Correct Option: D

Let the radius of new ball = R cm
then

	4	πR³ =	4	π (3³ + 4³ + 5³)
	3		3

R³ = 27 + 64 + 125 = 216
⇒ R = ³√6 × 6 × 6 = 6 cm