-
If the radius of a sphere is increased by 2 cm. its surface area increased by 352 cm². The radius of sphere before change is : use (π = 22/7)
-
- 3 cm
- 4 cm
- 5 cm
- 6 cm
- 3 cm
Correct Option: D
Let the radius of first sphere be r cm
and the radius of second sphere = (r + 2) cm
Now, Difference between surface area = 352
⇒ 4π {(r + 2)² – r²} = 352
or,
| 4 × | {(r + 2 -r) + (r + 2 + r)} = 352 | |
| 7 |
| ⇒ 2 × 2(r + 1) = | ||
| 4 × 22 |
| ⇒ r + 1 = | ||
| 4 × 4 × 22 |
⇒ r + 1 = 7
∴ r = 7 – 1 = 6 cm
