Montana Math MT.PLUS.ALG.EXP.3.b

MathGrades 9–12Exponential and Logarithmic Functions

The Standard

MT.PLUS.ALG.EXP.3
Understand that exponential and logarithmic functions can be represented using multiple forms by: Expressing exponential functions in the form f(x) = a · b^x and f(x) = Pe^(r·t), and Expressing logarithmic functions in base 10 and base e.
Understand that exponential and logarithmic functions can be represented using multiple forms by: Expressing logarithmic functions in base 10 and base e.

2026 Montana Mathematics Content Standards · Algebraic and Functional Reasoning

Teacher's field guide

What This Standard Means

What Students Need to Do

Students rewrite a logarithm using base 10 or base e. They use either form to find its value on a calculator.

What Mastery Looks Like

Given log₂(8), a student writes log(8)/log(2) and ln(8)/ln(2). They get 3 from either form and explain why the denominator uses the original base.

Common Misconceptions

Students may treat log(x) and ln(x) as the same function, or think ln(8) alone equals log₂(8). Some reverse the numerator and denominator when changing bases.

How to Assess It

On an exit ticket, ask students to rewrite log₄(64) using both log and ln, then evaluate it. Look for log(64)/log(4) = ln(64)/ln(4) = 3.

Lesson moves

Ways to Teach It

  1. Give pairs cards marked log₄(64), log(64)/log(4), ln(64)/ln(4), and 3; have them group equal values.

  2. Ask students to write two sentences explaining why ln(8) alone does not equal log₂(8).

  3. Run a whiteboard relay with log₅(125), log₃(81), and log₂(16); teams write both change-of-base forms.

  4. A bacteria count doubles to eight times its starting size; have students find the number of doublings with log(8)/log(2) and ln(8)/ln(2).

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