How do you do area of sector

Question

Area of sector JFK=70degree JD=7cm

Answer 1

A sector is some portion of a circle.

Formula for area of a circle is A =(pi)r²

 

For the area of some sector with x degrees lets use a proportional relationship

 

Area_sector               x degrees

____________   =       _____________

 

Area_circle                  360 degrees

 

(AREAsector)  = 70   

(pi) r²                  360

 

Solve by cross multiplication.

Answer 2

Hi, Abby!

 

A sector is simply a piece of a circle.  The easiest way to find the area of a sector is to find the area as if it were a complete circle (Area of a circle is pi*r².) and then multiply it by a ratio to represent the size of the sector compared to a whole circle (degree/360).

 

In your question, where JFK = 70 degrees and JD = 7cm, I am going to assume that JD is the diameter of what would be the whole circle (If it is the radius, then you can just use 7 for r).

 

radius = r = 1/2 * diameter = 1/2 * 7 = 3.5

 

Area = pi * r² * (degrees/360)

Area = 3.14 * (3.5)² * (70/360)

Area = 3.14 * 12.25 * 70/360

Area = 7.48 cm²

 

Hope this helps!

 

Patty