Section Warm-Up
In this section, we will be working with objects that do not have flat sides, but instead have circular surfaces. Let’s review what we already know about circles.
Think & Click: Section Warm-Up
Complete the Think & Click activity by looking at each problem below, thinking about it, and then clicking on the question to reveal the solution.
1. Imagine a ball, such as an orange or any spherical object. If you cut it through the middle, what is the shape of the cross section?
A circle
2. All formulas involving circles include what number?
π
3. What is the circumference of a circle?
C = 2πr = πd
4. What is the area of a circle?
A = πr²
5. What is the value of π?
π is about 3.14, but you should always use the ‘π’ key on your calculator.
6. If the circumference of a circle is 62.8319 in, what is the radius of the circle?
C = 2πr
62.8319 = 2πr *divide both sides by 2π.
10 = r
The radius is 10 in.
