Question

finding the area of a circle

find the radius of each circle. show your work.

1 12 in.
2 26 cm

find the area of each circle. write your answer using π.

3 20 yd

Explanation:

Step1: Recall radius - diameter relationship

The radius $r$ of a circle is half of its diameter $d$, i.e., $r=\frac{d}{2}$.

Step2: Calculate radius for circle 1

Given $d_1 = 12$ in, then $r_1=\frac{12}{2}=6$ in.

Step3: Calculate radius for circle 2

Given $d_2 = 26$ cm, then $r_2=\frac{26}{2}=13$ cm.

Step4: Calculate radius for circle 3

Given $d_3 = 20$ yd, then $r_3=\frac{20}{2}=10$ yd.

Step5: Recall area formula for circle

The area formula of a circle is $A = \pi r^{2}$.

Step6: Calculate area for circle 3

Substitute $r_3 = 10$ yd into the area formula, $A_3=\pi\times(10)^{2}=100\pi$ yd².

Answer:

1. $r = 6$ in
2. $r = 13$ cm
3. $A=100\pi$ yd²