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If the surface area of a sphere increased by 44%, find the percentage increase in...

Mathematics
JAMB 1989

If the surface area of a sphere increased by 44%, find the percentage increase in diameter
  • A. 44
  • B. 30
  • C. 22
  • D. 20
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Correct Answer: Option D
Explanation
Surface Area of Sphere A = 4\(\pi r^2\)

∴ A = 4\(\pi\)\(\frac{(D)^2}{2}\)

= \(\frac{(D)^2}{2}\)

= \(\pi\)D2

When increased by 44% A = \(\frac{144 \pi D^2}{100}\)

\(\pi\)\(\frac{(12D)^2}{10}\) = \(\pi\)\(\frac{(6D)^2}{5}\)

Increase in diameter = \(\frac{6D}{5}\) - D = \(\frac{1}{5}\)D

Percentage increase = \(\frac{1}{5}\) x \(\frac{1}{100}\)%

= 20%

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