Question

Find the circumference and area of the circle having the given diameter. Use 3.14 for pi.
dequals18.20 km
Question content area bottom
Part 1
The circumference is
  
enter your response here km.
​(Round to the nearest tenth as​ needed.)

Answer 1

To find the circumference and area of a circle given the diameter, you can use the following formulas:

1. **Circumference (C)**:
\[
C = \pi \times d
\]
where \( d \) is the diameter.

2. **Area (A)**:
\[
A = \pi \times r^2
\]
where \( r \) is the radius. (The radius is half of the diameter).

**Given:**
- Diameter \( d = 18.20 \) km

**Step 1: Calculate the circumference.**
Using \( \pi = 3.14 \):

\[
C = \pi \times d = 3.14 \times 18.20
\]
\[
C = 57.092 \text{ km}
\]

Now, round to the nearest tenth:
\[
C \approx 57.1 \text{ km}
\]

**Step 2: Calculate the area.**
First, find the radius:
\[
r = \frac{d}{2} = \frac{18.20}{2} = 9.10 \text{ km}
\]

Now use the area formula:
\[
A = \pi \times r^2 = 3.14 \times (9.10)^2
\]
\[
A = 3.14 \times 82.81 \approx 260.4874 \text{ km}^2
\]

Now, round to the nearest tenth:
\[
A \approx 260.5 \text{ km}^2
\]

**Final Results:**
- Circumference: **57.1 km**
- Area: **260.5 km²**