These worksheets give your students a review in solving for the unknown in logarithmic expressions.

How to Solve for the Unknown Logarithms? A logarithm is a concept which is effectively involved in the most advanced calculation. Especially in algebraic expressions, where unknown variables are provided in the form of logarithm functions. You may have witnessed equations like 4x = 16, which you can solve by simply asking yourself what power of 4 is 16? However, equations like 4x = 18 is are a bit more difficult. Yes, you can figure out that the value of x must be greater than 2. However, if you want to know the value of x with more precision, then you can use logarithms to find the answer. Now, how do we solve it? Let's take an example of 4x = 16; so that we know exactly what we want. 4x = 16. The next step is to take a log on both sides. Keep in mind when no base is written, then its 10. log 4⁡ x= log 16. Now, you can take the exponential property of log; which is log ab = bloga xlog⁡4 = log⁡16, x = log⁡16 / log⁡4, x = 1.204 / 0.602 = 2

In this section you will be given logarithmic equations and be asked to solve for a variable in the equation. The worksheets expect that you have worked with our logarithm conversion section or have a decent knowledge of that skill. The equations that you will be presented are single log problems with a missing variable that you are to complete. Also remember that both the log of zero and/or negative numbers is undefined. These worksheets explain how to solve for the unknown in logarithmic expressions. Though the formulas have been provided, students should already be familiar with the material.

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Solve For the Unknown Logarithm Worksheets

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Solve for the Unknown Logarithm Lesson and Practice

Students will practice solving for the unknown logarithm. This sample problem (logx 81 = -4 ) is solved and two practice problems are provided.


Students will solve for the unknown logarithm in each expression that is presented to them. Ten problems are provided.


Students will solve problems for the unknown logarithm. Ten problems are provided.

Review and Practice

This worksheet reviews how perform this skill in a whole and fractional situation. A sample problem is solved and six practice problems are provided.


Students demonstrate their proficiency with finding unknown values within logarithms. Ten problems are provided.


Students will solve these problems and show us where they stand with this skill. Three problems are provided, and space is included for students to copy the correct answer when given.