If three spheres of radius 75 cm, 60 cm and 45 cm are melted into one big sphere, then the radius of the big sphere is:
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 90 cm.
Let the radius of the big sphere = R cm
(4/3)πR3 = (4/3)π(75)3 + (4/3)π(60)3 + (4/3)π(45)3
⇒ R3 = (75)3 + (60)3 + (45)3 = 421875 + 216000 + 91125 = 729000
⇒ R = ³√729000 = 90 cm