Question

Find the area of a circle with a diameter of

22 millimeters. Round to the nearest tenth.
A 380.1 mm2
B 319.5 mm2
C 189.9 mm2
D 69.1 mm?

Answer 1

A. 380.1 mm²

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

Geometry

Area of a Circle Formula: A = πr²

• r is radius

Radius Formula:
`\displaystyle r = (d)/(2)`

• d is diameter

Explanation:

Step 1: Define

Identify variables

d = 22 mm

Step 2: Derive

Rewrite formula

1. [Area of a Circle Formula] Substitute in r [Radius Formula]:
   `\displaystyle A = \pi ((d)/(2))^2`
2. Evaluate exponents:
   `\displaystyle A = \pi ((d^2)/(4))`
3. Multiply:
   `\displaystyle A = (\pi d^2)/(4)`

Step 3: Solve for A

1. Substitute in variables [Modified Area of a Circle Formula]:
   `\displaystyle A = (3.14(22 \ mm)^2)/(4)`
2. Evaluate exponents:
   `\displaystyle A = (3.14(484 \ mm^2))/(4)`
3. Multiply:
   `\displaystyle A = (1520.53 \ mm^2)/(4)`
4. Divide:
   `\displaystyle A = 380.133 \ mm^2`
5. Round:
   `\displaystyle A \approx 380.1 \ mm^2`