Question

find the circumference of each circle using the formula $c = 2\pi r$. the variable $r$ stands for radius. use 3.14 for $\pi$ (in.).

1. circle with diameter 15 cm
2. circle with diameter 6 yd
3. circle with radius 13 ft
4. circle with radius 26 m
5. circle with radius 62 ft
6. circle with radius 36 yd

Explanation:

Step1: Identify radius for Circle 1

The given length is diameter ($d=15$ cm), so $r=\frac{15}{2}=7.5$ cm.

Step2: Calculate circumference for Circle 1

Use $C=2\pi r$, substitute $\pi=3.14$, $r=7.5$:
$C=2\times3.14\times7.5=47.1$ cm

Step3: Identify radius for Circle 2

The given length is diameter ($d=6$ yd), so $r=\frac{6}{2}=3$ yd.

Step4: Calculate circumference for Circle 2

Use $C=2\pi r$, substitute $\pi=3.14$, $r=3$:
$C=2\times3.14\times3=18.84$ yd

Step5: Identify radius for Circle 3

The given length is diameter ($d=13$ ft), so $r=\frac{13}{2}=6.5$ ft.

Step6: Calculate circumference for Circle 3

Use $C=2\pi r$, substitute $\pi=3.14$, $r=6.5$:
$C=2\times3.14\times6.5=40.82$ ft

Step7: Identify radius for Circle 4

Given radius $r=26$ m.

Step8: Calculate circumference for Circle 4

Use $C=2\pi r$, substitute $\pi=3.14$, $r=26$:
$C=2\times3.14\times26=163.28$ m

Step9: Identify radius for Circle 5

Given radius $r=62$ ft.

Step10: Calculate circumference for Circle 5

Use $C=2\pi r$, substitute $\pi=3.14$, $r=62$:
$C=2\times3.14\times62=389.36$ ft

Step11: Identify radius for Circle 6

Given radius $r=36$ yd.

Step12: Calculate circumference for Circle 6

Use $C=2\pi r$, substitute $\pi=3.14$, $r=36$:
$C=2\times3.14\times36=226.08$ yd

Answer:

1. $47.1$ cm
2. $18.84$ yd
3. $40.82$ ft
4. $163.28$ m
5. $389.36$ ft
6. $226.08$ yd