5a. A circle has a circumference of 131.95 meters. What is the diameter and how did you calculate it?

C = πd


You must show ALL work for full credit.

(2 points)
5b. What is the area for the same circle? How did you calculate it?

A = πr2


You must show ALL work for full credit.

(2 points)

1 answer

To solve both parts of the problem, we will use the relationships between circumference, diameter, radius, and area of a circle.

5a. Calculate the Diameter

The formula for the circumference \( C \) of a circle is given by:

\[ C = \pi d \]

Where:

  • \( C \) is the circumference,
  • \( d \) is the diameter,
  • \( \pi \) (pi) is approximately \( 3.14159 \).

We know the circumference \( C \) is 131.95 meters, so we can rearrange the formula to solve for the diameter \( d \):

\[ d = \frac{C}{\pi} \]

Plugging in the value of \( C \):

\[ d = \frac{131.95}{\pi} \approx \frac{131.95}{3.14159} \approx 42.00 \text{ meters} \]

Thus, the diameter of the circle is approximately 42.00 meters.

5b. Calculate the Area

To calculate the area \( A \) of the same circle, we use the formula:

\[ A = \pi r^2 \]

Where:

  • \( A \) is the area,
  • \( r \) is the radius of the circle.

Since the radius \( r \) is half of the diameter \( d \):

\[ r = \frac{d}{2} = \frac{42.00}{2} = 21.00 \text{ meters} \]

Now we can plug the radius into the area formula:

\[ A = \pi r^2 = \pi (21.00)^2 \]

Calculating \( (21.00)^2 \):

\[ (21.00)^2 = 441.00 \]

Now substituting back into the area formula:

\[ A = \pi \times 441.00 \approx 3.14159 \times 441.00 \approx 1385.44 \text{ square meters} \]

Thus, the area of the circle is approximately 1385.44 square meters.

Summary:

  • Diameter: 42.00 meters
  • Area: 1385.44 square meters