area of a circle

Question

Sasha measures circle A and circle B. The diameter of Circle B is 12 centimeters, and the diameter of Circle A is 6 centimeters. Sasha wants to calculate the area of each circle.

 

A) what is the area of each circle, expressed in terms of π (pie)

 

B) how many times greater is the area of a circle if its diameter is doubled?

Answer 1

A=(pi)*r²

A=(pi)*6² (if the diameter is 12 the radius is 6)

A=(pi)*36

A=36Π sq cm

A=(pi)*3² (the radius is half the diameter)

A=(pi)*9

A=9Π sq cm

 

if the diameter is doubled the area is quadrupled (4 times as large)

6²=(2*3)²=2²*3²=4*9

3²=(1*3)²=1²*3²=1*9

 

Answer 2

area = πr²

radius = 1/2 of the diameter

Circle A has a diameter of 6 therefore its radius is 3

Area = π3² = 9π square centimeters

 

radius = 1/2 of the diameter
Circle B has a diameter of 12 therefore its radius is 6
Area = π6² = 36π square centimeters

 

If the diameter is doubled the area is quadrupled.

 

Diameter doubles from 6 to 12 and the area quadrupled from 9π to 36π