The circumference of a circle is 125.6
kilometers. What is the circle's radius?

r = 20 km

General Formulas and Concepts:

Symbols

π (pi) ≈ 3.14

Pre-Algebra

Order of Operations: BPEMDAS

Brackets Parenthesis Exponents Multiplication Division Addition Subtraction Left to Right  

Equality Properties

Multiplication Property of Equality Division Property of Equality Addition Property of Equality Subtraction Property of Equality

Geometry

Circumference of a Circle Formula: C = 2πr

r is radius

Step-by-step explanation:

Step 1: Define

Identify variables

C = 125.6 km

Step 2: Solve for r

Substitute in variables [Circumference of a Circle Formula]:                        125.6 km = 2(3.14)rMultiply:                                                                                                             125.6 km = 6.28r[Division Property of Equality] Divide 6.28 on both sides:                            20 km = rRewrite:                                                                                                             r = 20 km