# Lesson 9

Applying Area of Circles

Let’s find the areas of shapes made up of circles.

### Problem 1

A circle with a 12-inch diameter is folded in half and then folded in half again. What is the area of the resulting shape?

### Problem 2

Find the area of the shaded region. Express your answer in terms of $$\pi$$.

### Problem 3

The face of a clock has a circumference of 63 in. What is the area of the face of the clock?

(From Unit 3, Lesson 8.)

### Problem 4

Which of these pairs of quantities are proportional to each other? For the quantities that are proportional, what is the constant of proportionality?

1. Radius and diameter of a circle
2. Radius and circumference of a circle
3. Radius and area of a circle
4. Diameter and circumference of a circle
5. Diameter and area of a circle
(From Unit 3, Lesson 7.)

### Problem 5

Find the area of this shape in two different ways.

(From Unit 3, Lesson 6.)

### Problem 6

$$e$$
$$j$$
2. Here is an equation for the table: $$j = 1.25e$$. What does the 1.25 mean?
3. Write an equation for this relationship that starts $$e = \text{...}$$