Question

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

Answer 1

197.29

Explanation:

Multiple the circumfernece by 3.14 and then divide that number by 2.

Answer 2

r = 20 km

General Formulas and Concepts:

Symbols

• π (pi) ≈ 3.14

Pre-Algebra

Order of Operations: BPEMDAS

1. Brackets
2. Parenthesis
3. Exponents
4. Multiplication
5. Division
6. Addition
7. 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

Explanation:

Step 1: Define

Identify variables

C = 125.6 km

Step 2: Solve for r

1. Substitute in variables [Circumference of a Circle Formula]: 125.6 km = 2(3.14)r
2. Multiply: 125.6 km = 6.28r
3. [Division Property of Equality] Divide 6.28 on both sides: 20 km = r
4. Rewrite: r = 20 km