MCQ
A largest sphere of radius 3.5 cm is carved out from a cubical solid. The difference between their surface areas is
  • A
    $224 cm^2$
  • $140 cm^2$
  • C
    $176 cm^2$
  • D
    $80.5 cm^2$

Answer

Correct option: B.
$140 cm^2$
(B) $140 cm^2$
We have, $r=$ radius of the sphere $=3.5 cm$
$\therefore \quad a=\text { Length of an edge of the cubical solid }=2 r=7 cm$
Hence, required difference
$=6 a^2-\frac{4}{3} \pi r^3=6 \times 7^2-4 \times \frac{22}{7} \times\left(\frac{7}{2}\right)^2=(294-154) cm ^2  = 140 cm^2$

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