10 identical solid spherical balls of radius 3 cm are melted to form a single sphere. In this process 20% of solid is wasted. What is the radius (in cm) of the bigger sphere ?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 ie 6.
Volume of 10 balls = 10 × (4/3) × π × 33
= 10 × 4 × 9 × π = 1131.42
Remaining volume = 0.8 × 1131.42 = 905.14
905.14 = (4/3) × π × (R)3
R3 = (905.14 × 3 × 7)/88 = 216
R = 6