### Home > GC > Chapter 8 > Lesson 8.3.3 > Problem8-107

8-107.

Use what you know about the area and circumference of circles to answer the questions below. Show all work. Leave answers in terms of π.

1. If the radius of a circle is $14$ units, what is its circumference? What is its area?

Remember that the area of a circle is $\pi r^2$, while the circumference of a circle is $2\pi r$.

area = $196\pi$
circumference = $28\pi$

2. If a circle has diameter $10$ units, what is its circumference? What is its area?

Use the formulas given in part (a). What is the radius of this circle?

3. If a circle has circumference $100\pi$ units, what is its area?

$100\pi = 2\pi r$
Solve for the radius then use the radius to calculate the area.