KKhaemenes PrecalculusOpen-Age · Printable Analytical Lesson
Unit 03Course HomeTeacher Key

Unit 03 · Lesson 01 · Week 7 · Exponential & Logarithmic Functions

Exponential Growth, Decay & Percent Change

Model multiplicative change with exponential functions and interpret growth factors, percent rates, doubling time, half-life, and continuous change. In this lesson, the central focus is exponential growth, decay & percent change. Learners move among symbolic, graphical, numerical, and contextual evidence rather than relying on one representation alone.

Open-AgePrintableFoundation · Core · ExtendedMastery target 80%

Learning intentions

  • Interpret the defining quantities and notation used in exponential growth, decay & percent change.
  • Construct or analyze at least two representations related to exponential growth, decay & percent change.
  • Show symbolic work with correct domains, units, intervals, or angle measures.
  • Explain why the selected method is valid and check the result against another representation.

Essential question

How do multiplicative change, inverse structure, logarithmic scales, and parameter interpretation support defensible growth and decay models?

Multiple-representation model

Exponential visualModel multiplicative change with exponential functions and interpret growth factors, percent rates, doubling time, half-life, and continuous change. xy

Model multiplicative change with exponential functions and interpret growth factors, percent rates, doubling time, half-life, and continuous change.

A=A_0(1+r)^tA=A_0e^{kt}t_d=\frac{\ln2}{k}

Worked reasoning

Growth modelA 6% annual increase is modeled by A=A₀(1.06)^t, not A=A₀+0.06t.
Inverse reasoningTo solve 5e^{0.3t}=42, isolate the exponential and apply ln: t=ln(42/5)/0.3.

Misconception check: A constant percent change is multiplicative, not additive; equal time intervals multiply by the same factor.

Communication and reasoning

Write a complete response that identifies the representation used, shows the symbolic steps, interprets parameters or units, and verifies the conclusion with a second representation or reasonableness check.

Khaemenes Academy · Open-Age Precalculus

Exponential Growth, Decay & Percent Change

Analyze, calculate, graph, or justify each result. Show reasoning, intervals, units, and calculator evidence when used.

U03 · L01
Name
Date
1

A quantity begins at 500 and grows 4% yearly. Write the model.

Exponential visualModel multiplicative change with exponential functions and interpret growth factors, percent rates, doubling time, half-life, and continuous change. xy
2

Evaluate 200(0.8)^3.

Exponential visualModel multiplicative change with exponential functions and interpret growth factors, percent rates, doubling time, half-life, and continuous change. xy
3

A population doubles every 6 years. Give a base-2 model.

Exponential visualModel multiplicative change with exponential functions and interpret growth factors, percent rates, doubling time, half-life, and continuous change. xy
4

Solve 3^x=81.

Exponential visualModel multiplicative change with exponential functions and interpret growth factors, percent rates, doubling time, half-life, and continuous change. xy
5

Find the continuous growth rate k if A=A₀e^{0.07t}.

Exponential visualModel multiplicative change with exponential functions and interpret growth factors, percent rates, doubling time, half-life, and continuous change. xy
6

Find the half-life for A=A₀e^{-0.2t}.

Exponential visualModel multiplicative change with exponential functions and interpret growth factors, percent rates, doubling time, half-life, and continuous change. xy
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