Three solid metallic spheres whose radii are 1 cm, x cm, and 8 cm, are melted and recast into a single solid sphere of diameter 18 cm. The surface area (in cm²) of the sphere with radius x cm is?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 ie 144 π .
V = (4/3) π R³ = (4/3) π (r13 + r23 + r33)
9³ = 1³ + x³ + 8³
x³ = 729 - 513
x = 6
S.A.= 4πr²
= 4π × 36
= 144π