Circumference of circle and area of circle

Question

Calculate  (a) circumference of circle of radius 3.5cm and  (b) area of circle of radius 4.65cm

Answer 1

Hi Ajay,

To find the circumference of given radius of 3.5 cm the following applies: 

Circumference = Diameter * pi 

To find the diameter of a circle you multiply the radius by 2 

Therefore: 

Diameter = 3.5 * 2 
Diameter = 7 cm 

Therefore: 

Circumference = Diameter * pi

Circumference = 7 * pi 
                     = 7 * 3.14
                     = 21.98 

Circumference ≅ 21.98      *The reason I use the 'approximately equal to' sign is due to pi. If your teacher wants you to use the equal sign, just use it. 

To determine the area of the circle with given radius of 4.65 cm you use the following: 

A = pi * r^2
   <sup>= 3.14 * (4.65)^2
    = 3.14 *21.62
     = 67.87 squared cm (I rounded up) 

Hope this helps. Have a great day today and let me know if I can assist further.</sup>