GRE Subject Test: Math : Logarithms

Study concepts, example questions & explanations for GRE Subject Test: Math

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Example Questions

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Example Question #1 : Evaluating Logarithms

Solve: 

Possible Answers:

Correct answer:

Explanation:

Step 1: Re-write the log equation as an exponential equation. To do this, take the base of the log function and raise it to the number on the right side of the equal sign. This new exponent is equal to the number to the right of the log base.



Step 2: Re-write the right hand side as a power of 4..



Step 3: Re-write the equation



Step 4: We have the same base, so we can equal the exponents..

Example Question #2 : Logarithms

Possible Answers:

Correct answer:

Explanation:

In order to solve for x, we must first rewrite the log in exponential form. 

Every log is written in the below general form: 

In this case we have: 

This becomes: 

We can solve this by taking the square root of both sides: 

 

 

Example Question #3 : Logarithms

Solve for

Possible Answers:

Correct answer:

Explanation:

Use rules of logarithms...

Take the base of the log and raise it to the number on the right side of the equal sign (which becomes the exponent):

Example Question #4 : Logarithms

Evaluate: 

Possible Answers:

Correct answer:

Explanation:

Step 1: Write the expression in exponential form...

Given: 

Step 2: Convert the right hand side into a power of 6..

Step 3: Re-write the equations...

Since the bases are equal, taking log of both sides will cancel them.

Example Question #5 : Logarithms

Possible Answers:

Correct answer:

Explanation:

Example Question #121 : Algebra

Rewrite the following expression as a single logarithm

Possible Answers:

Correct answer:

Explanation:

Recall a few properties of logarithms:

1.When adding logarithms of like base, we multiply the inside.

2.When subtracting logarithms of like base, we divide the inside.

3. When multiplying a logarithm by a number, we can raise the inside to that power.

So we begin with this:

I would start with 3 to simplify the first log.

Next, use rule 1 on the first two logs.

Then, use rule 2 to combine these two.

So our answer is 6.06.

Example Question #1 : Logarithms

Possible Answers:

Correct answer:

Explanation:

When combining logarithms into one log, we must remember that addition and multiplication are linked and subtraction and division are linked. 

In this case we have multiplication and division - so we assume anything that is negative, must be placed in the bottom of the fraction. 

 

 

Example Question #8 : Logarithms

Possible Answers:

Correct answer:

Explanation:

When rewriting an exponential function as a log, we must follow the model below: 

A log is used to find an exponent. The above corresponds to the exponential form below: 

Example Question #9 : Logarithms

Possible Answers:

Correct answer:

Explanation:

In order to rewrite a log, we must remember the pattern that they follow below: 

In this question we have: 

 

Example Question #10 : Logarithms

Express  as a single logarithm. 

Possible Answers:

Correct answer:

Explanation:

Step 1: Recall all logarithm rules:

Step 2: Rewrite the first term in the expression..

Step 3: Re-write the third term in the expression..

Step 4: Add up the positive terms...

Step 5: Subtract the answer the other term from the answer in Step 4.

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