Ex 13.4, 9
Assume π = 22/7, unless stated otherwise.
A right circular cylinder just encloses a sphere of radius r . Find
surface area of the sphere,
Radius of sphere = r
Surface Area of sphere = 4πr2
Ex 13.4, 9
Assume π = 22/7, unless stated otherwise.
A right circular cylinder just encloses a sphere of radius r . Find
(ii) curved surface area of the cylinder,
Curved Surface area of cylinder = 2𝜋rh
Radius of cylinder = r
It can be seen that
Height of cylinder is twice the radius
Height of cylinder (h)= r + r = 2r
Curved Surface area of cylinder = 2𝜋rh
= 2𝜋r(2r)
= 4𝜋r2
Ex 13.4, 9
Assume π = 22/7, unless stated otherwise.
A right circular cylinder just encloses a sphere of radius r . Find
(iii) ratio of the areas obtained in (i) and (ii).
Ratio = (𝑆𝑢𝑟𝑓𝑎𝑐𝑒 𝐴𝑟𝑒𝑎 𝑜𝑓 𝑠𝑝ℎ𝑒𝑟𝑒 𝑜𝑏𝑡𝑎𝑖𝑛𝑒𝑑 𝑖𝑛 (𝑖))/(𝑆𝑢𝑟𝑓𝑎𝑐𝑒 𝐴𝑟𝑒𝑎 𝑜𝑓 𝑐𝑦𝑙𝑖𝑛𝑑𝑒𝑟 𝑜𝑏𝑡𝑎𝑖𝑛𝑒𝑑 𝑖𝑛 (𝑖𝑖))
= (4𝜋𝑟^2)/(4𝜋𝑟^2 )
= 1/1
So the ratio is 1 : 1

Made by

Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 12 years. He provides courses for Maths and Science at Teachoo.