A solid sphere of diameter 7 cm is cut into two equal halves. What will be the increase in its total surface area?
Answer & explanation
Correct answer: option 1
We have,
Diameter = 7
Then the radius (r) = \(\frac{7}{2}\) = 3.5
Initial surface area = 4πr2 = 4 π (3.5)2
Final surface area = 4πr2 + 2 π r2
Final surface area = 6πr2
Increase in total surface area = 6πr2 - 4πr2 = 2πr2
Increase in total surface area = 2π(3.5)2 = 2 × \(\frac{7}{2}\) × (3.5)2 = 76.96 = 77cm2