Mensuration

 

 

 

Contents

 

Parts of Circle

 

Area of Circle

 

Area of Sector & Length of Arc

 

Area of Triangle 

 

Volume of Cylinder

 

Surface Area of Cylinder

 

Volume of Cones & Pyramids

 

Surface Area of Cones & Pyramids

 

Volume of Sphere

 

Surface Area of Sphere

  

Quiz

 

 

Geometry Main Page

Surface Area of Sphere

Archimedes, a Greek mathematician, found out that the surface area of a sphere is the same as the curved surface area of a cylinder having the same diameter as the sphere and a height same length as the diameter. 

 

Curved surface area of cylinder = 2prh
                                            = 2pr(2r)
                                            = 4pr2 
 
Thus the surface area of a sphere with radius r = 4 pr2 

Example 1

A solid sphere has a radius of 3m. Calculate its surface area. (Take p = 22/7)

Surface area = 4 pr2  
                  = 4 x 22/7 x 3 x 3
                  = 113m2 (3 s.f.)

Example 2
 
Find the radius of a sphere with a surface area of 
64p m2 
 
Surface area = 4 pr2 
64p = 4pr2
16 = r2 
  r  = 4cm
 
The radius is 4cm.