The ratio of the total surface area and volume of a sphere is 2 : 7. Its radius is :
Show answer & explanation
Correct answer: C
Explanation
The correct answer is Option 3 i.e. 10.5 cm.
We know that,
The total surface area of the sphere = 4πr2
Volume of a sphere = (4/3)πr3
where, r = Radius of sphere
According to the question,
The ratio of the total surface area and volume of a sphere is 2 : 7
(4πr2)/(4/3πr3) = 2/7
⇒ 3/r = 2/7
⇒ r = 21/2 = 10.5 cm
Thus,
The radius of the sphere is 10.5 cm