Area of a circle with radius "r" can be found using the formula :
[tex] Area = \pi r^{2} [/tex]
Also we have radius = diameter / 2
So let us find area of all the given diameter or radius.
(1)
we are given diameter =5cm
So first finding radius, radius = diameter/2 =5/2 =2.5
Now plugging this value of radius in the formula for area we have,
[tex] Area = \pi (2.5)^{2} [/tex]
[tex] Area = 3.14 * 6.25 [/tex]
Area =19.625 cm² or Area =19.63 cm²
So first answer is correct
(2)
radius =3cm
Plugging this value in the formula for area ,
[tex] Area = \pi r^{2} [/tex]
[tex] Area = 3.14* (3)^{2} [/tex]
[tex] Area = 3.14*9 [/tex]
Area =28.26cm²
(3)
Diameter =4cm
Radius = 4/2 =2 cm
[tex] Area = \pi r^{2} [/tex]
[tex] Area = 3.14* 2^{2} [/tex]
Area =12.56 cm²
(4)
Radius =7cm
[tex] Area = \pi r^{2} [/tex]
[tex] Area = 3.14 * 7^{2} [/tex]
[tex] Area = 3.14 * 49 [/tex]
Area =153.86 cm²
