A hemisphere of radius 30 cm is moulded to form a cylinder of height 180 cm. The diameter of the cylinder is:
Answer & explanation
Correct answer: option 4
We know that,
Volume of hemisphere = \(\frac{2}{3}\) πr3
Volume of cylinder = πR2h
We have,
Radius = r = 30 cm
Height = h = 180 cm
According to the question,
πR2h = \(\frac{2}{3}\) πr3
= R2 × 180 = \(\frac{2}{3}\) × 30 × 30 × 30
= R2 = \(\frac{54000}{540}\)
= R2 = 100
= R = 10 cm
Then, Diameter of the cylinder = 2 × 10 = 20 cm