Question

What's the area of a circle with diameter 18 units? Question 8 options: A) 9π units2 B) 81π units2 C) π units2 D) 18π units2

Answer 1

B) 81π units²

General Formulas and Concepts:

Pre-Algebra

Order of Operations: BPEMDAS

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

• Left to Right

Geometry

Radius of a Circle Formula: r = d/2

• r is radius
• d is diameter

Area of a Circle Formula: A = πr²

Explanation:

Step 1: Define

Diameter d = 18 units

Step 2: Manipulate Variables

Radius r = 18 units/2 = 9 units

Step 3: Find Area

1. Substitute in r [Area of a Circle Formula]: A = π(9 units)²
2. [Area] Evaluate exponents: A = π(81 units²)
3. [Area] Multiply: A = 81π units²