Number and Quantity

learning_notes

Last updated: 8/16/2025

Real and Complex Numbers

Key Concepts

  • Properties of integers, rational, and irrational numbers
  • Order of operations (PEMDAS)
  • Absolute value, square roots, and radicals
  • Operations with complex numbers (e.g., i^2 = -1)

Skills Tested

  • Simplifying expressions with real or complex numbers
  • Performing operations like addition, subtraction, multiplication, and division on complex numbers
  • Understanding number classifications (e.g., identifying if a result is rational or irrational)

Example Question

Simplify: (3 + 4i)(2 - i) A. 6 - 3i + 8i - 4i^2 B. 6 + 5i + 4 C. Answer: 10 + 5i (Because -4i^2 = +4)

Ratios, Rates, and Proportions

Key Concepts

  • Setting up and solving proportions
  • Unit rates (e.g., miles per hour, cost per item)
  • Scaling (e.g., similar figures, map scale)

Skills Tested

  • Translating real-world scenarios into mathematical ratios
  • Solving proportions using cross-multiplication
  • Interpreting unit conversions

Example Question

A recipe that serves 4 people calls for 3 cups of flour. How many cups are needed to serve 10 people? A. 6 B. 7.5 C. Answer: 7.5 (Set up ratio: \frac{3}{4} = \frac{x}{10} \Rightarrow x = 7.5)

Scientific Notation and Significant Figures

Key Concepts

  • Converting between standard and scientific notation
  • Multiplying/dividing numbers in scientific notation
  • Estimating using powers of ten

Skills Tested

  • Performing operations with scientific notation
  • Recognizing equivalent expressions
  • Estimating large/small quantities

Example Question

(3 \times 10^4) \times (2 \times 10^3) = ? A. 6 \times 10^7 B. Answer: 6 \times 10^7 (Multiply coefficients: 3 \times 2 = 6; add exponents: 4 + 3 = 7)

Quantities and Units

Key Concepts

  • Unit conversions (e.g., inches to feet, minutes to hours)
  • Dimensional analysis (canceling units)
  • Understanding and using compound units (e.g., mi/hr, kg/m²)

Skills Tested

  • Converting between different measurement systems
  • Setting up and interpreting unit-based problems
  • Making sense of units in formulas

Example Question

If a car travels 180 miles in 3 hours, what is its speed in feet per second? (1 mile = 5280 feet) A. 88 ft/s B. Answer: 88 ft/s (180 miles ÷ 3 hours = 60 mi/hr → convert: 60 \times \frac{5280}{3600} = 88)

Rational and Irrational Numbers

Key Concepts

  • Rational numbers: can be written as a fraction
  • Irrational numbers: non-repeating, non-terminating decimals (e.g., \pi, \sqrt{2})
  • Properties of number types under operations

Skills Tested

  • Identifying number types
  • Predicting results of operations (e.g., rational × irrational = irrational?)
  • Working with square roots

Example Question

Which of the following is irrational? A. \frac{7}{3} B. \sqrt{49} C. \sqrt{2} Answer: C. \sqrt{2} (It is non-repeating, non-terminating)

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