Volumes Practice Test 1

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Question : 29 of 40

Marks: +1, -0

If the radius of a sphere is increased by 2 cm, then its surface area increases by 352

cm^2

. Find the radius of the original sphere.

3 cm
6 cm
9 cm
12 cm

Solution:

Here,

4π(r+2)^2

=

4πr^2 + 352

⇒

4π(r^2 + 4r+4)

=

4πr^2 + 352

⇒

4πr^2 + 16πr+16π

=

4πr^2 + 352

⇒

16× {22}/7 (r+1)

= 352
⇒ r + 1 =

{352×7}/{16×22}

= 7
⇒ r = 7 – 1 = 6 cm

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