Question on: JAMB Mathematics - 2009
Find the radius of a sphere whose surface area is 154cm2.
A
7.00cm
B
3.50cm
C
3.00cm
D
1.75cm
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Correct Option: B
Surface area of a sphere = 4\(\pi\)r2
4\(\pi\)r2 = 154 cm2
\(\pi\)r2 = \(\frac{154}{4}\)
= 38.5
\(\pi\)r2 = 38.5
r2 = 38.5 + \(\frac{22}{7}\) \(\to\) r2 = 38.5 x \(\frac{7}{22}\)
r2 12.25 \(\to\) r = \(\sqrt{12.25}\)
= 3.5 cm
4\(\pi\)r2 = 154 cm2
\(\pi\)r2 = \(\frac{154}{4}\)
= 38.5
\(\pi\)r2 = 38.5
r2 = 38.5 + \(\frac{22}{7}\) \(\to\) r2 = 38.5 x \(\frac{7}{22}\)
r2 12.25 \(\to\) r = \(\sqrt{12.25}\)
= 3.5 cm
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