And now back to our study of geometry, although we take a quick break from the polygons of lessons past. (Or is a circle a polygon with an infinite number of sides? ... I'll let you decide.)
On last year's tests, there were 13 questions about circles, with the median placement at question # 55.
Number Dojo Level: 157
Let's start with a few definitions:
- Radius (r): the distance from a circle's center to its edge
- Diameter (d): the greatest distance across a circle (from one edge to the opposite edge)
- Circumference (C): the distance around a circle--its perimeter
- Area (A): the amount of space contained within a circle's edge
- Pi (π): our favorite mathematical constant--irrational but real--equal to the ratio of a circle's circumference to its diameter. Approximately 3.14159265358979323846264338327950288419716939937510...
And a few formulas:
Example 1: The area of a circle with a radius of 9 is kπ; k = ___
Example 2: The circumference of a circle with a radius of 17 is kπ; k = ___
Example 3: What is the diameter of a circle with a circumference of 14π? ___
Example 4: What is the radius of a circle with a circumference of 64π? ___
Example 5: * The area of a circle with a radius 12 = ___
Example 6: * The circumference of a circle with radius 25 is ___