ACT Math : How to find a logarithm

Study concepts, example questions & explanations for ACT Math

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Example Questions

Example Question #21 : How To Find A Logarithm

If , then  ?

Possible Answers:

4

5

10

25

15

Correct answer:

5

Explanation:

 

Calculate the power of  that makes the expression equal to 25. We can set up an alternate or equivalent equation to solve this problem:

Solve this equation by taking the square root of both sides. 

, because logarithmic equations cannot have a negative base.

The solution to this expression is:

 

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