Exponential Modeling and Logarithms

Lesson 8

Math

Unit 5

11th Grade

Lesson 8 of 16

Objective


Describe and evaluate simple numeric logarithms (Part II).

Common Core Standards


Core Standards

  • F.LE.A.4 — For exponential models, express as a logarithm the solution to abct = d where a, c, and d are numbers and the base b is 2, 10, or e; evaluate the logarithm using technology.

Foundational Standards

  • N.RN.A.1
  • N.RN.A.2

Criteria for Success


  1. Explain why fractional arguments in logarithms correspond to roots using properties of exponents.
  2. Explain why negative exponents correspond to reciprocals using properties of exponents.
  3. Evaluate numeric logarithms to fractions and negative numbers.

Tips for Teachers


This lesson extends logarithms from whole numbers to fractions and negative numbers, and serves largely as practice to build fluency after being introduced to logarithms in the last lesson.

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Anchor Problems


Problem 1

Using the integers 1 to 9, fill in the red and blue boxes so that the chart is accurate. You can only use a number once per red box and once per blue box.

Guiding Questions

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References

Open Middle Logs

Logs by is made available on Open Middle under the CC BY-NC-SA 4.0 license. Accessed Feb. 22, 2018, 4:40 p.m..

Problem 2

The graph below shows the function $${f(x)=4^x}$$

Find each value:

$${f(-1)}$$

$${f(-3)}$$

$${f\left ( 1\over2 \right )}$$

$${f\left ( 3\over2 \right )}$$

Find each value:

$${\mathrm{log}_4{1\over4}}$$

$${\mathrm{log}_4{1\over64}}$$

$${\mathrm{log}_42}$$

$${\mathrm{log}_48}$$

Guiding Questions

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Target Task


Problem 1

Explain why $${\mathrm{log}_23>\mathrm{log}_32}$$.

Problem 2

Evaluate each log:

$${\mathrm{log}_927}$$

$${\mathrm{log}_{1\over10}1000d}$$

Additional Practice


The following resources include problems and activities aligned to the objective of the lesson that can be used for additional practice or to create your own problem set.

  • Write a logarithm that evaluates to a fraction. 
  • Write a logarithm that evaluates to a negative number. 
  • Include problems translating between logarithm form and exponential form.
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Lesson 7

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Lesson 9

Lesson Map

A7CB09C2-D12F-4F55-80DB-37298FF0A765

Topic A: Modeling with and Interpreting Exponential Functions

Topic B: Definition and Meaning of Logarithms

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