ACT Math : Algebra

Study concepts, example questions & explanations for ACT Math

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Example Questions

Example Question #3 : Logarithms

Evaluate 

log327

Possible Answers:

10

9

30

3

27

Correct answer:

3

Explanation:

You can change the form to 

3x = 27

= 3

Example Question #1 : Logarithms

If \small \log_{x}49=2, what is \small x?

Possible Answers:

2401

24.5

10

0

7

Correct answer:

7

Explanation:

If \small \log_{x}y=z, then \small x^{z}=y

\small x^{2}=49

\small x=7

Example Question #1 : Logarithms

If log4  x = 2, what is the square root of x?

Possible Answers:

16

4

2

3

12

Correct answer:

4

Explanation:

Given log4= 2, we can determine that 4 to the second power is x; therefore the square root of x is 4.

Example Question #2 : Logarithms

Solve for x in the following equation:

log224 - log23 = logx27

Possible Answers:

2

1

9

3

2

Correct answer:

3

Explanation:

Since the two logarithmic expressions on the left side of the equation have the same base, you can use the quotient rule to re-express them as the following:

log224  log23 = log2(24/3) = log28 = 3

Therefore we have the following equivalent expressions, from which it can be deduced that x = 3.

logx27 = 3

x3 = 27

Example Question #2 : Logarithms

What value of  satisfies the equation ?

Possible Answers:

Correct answer:

Explanation:

The answer is .

 can by rewritten as .

In this form the question becomes a simple exponent problem. The answer is  because .

Example Question #4 : Logarithms

If , what is  ?

Possible Answers:

Correct answer:

Explanation:

Use the following equation to easily manipulate all similar logs:

 changes to .

Therefore,  changes to .

2 raised to the power of 6 yields 64, so must equal 6. If finding the 6 was difficult from the formula, simply keep multiplying 2 by itself until you reach 64.

Example Question #5 : Logarithms

Which of the following is a value of x that satisfies \log_{x}64=2 ?

Possible Answers:

2

4

16

32

8

Correct answer:

8

Explanation:

The general equation of a logarithm is \log_{x}a=b, and x^{b}=a

In this case, x^{2}=64, and thus x=8 (or -8, but -8 is not an answer choice)

Example Question #791 : Algebra

How can we simplify this expression below into a single logarithm?

 

 

Possible Answers:

 

Cannot be simplified into a single logarithm

Correct answer:

Explanation:

Using the property that  , we can simplify the expression to .

Given that  and

We can further simplify this equation to 

 

 

 

Example Question #101 : Exponents

What is the value of ?  Round to the nearest hundredth.

Possible Answers:

Correct answer:

Explanation:

You could solve this by using your calculator. Remember that you will have to translate this into:

Another way you can solve it is by noticing that 

This means you can rewrite your logarithm:

Applying logarithm rules, you can factor out the power:

For any value . Therefore, . So, your answer is .

Example Question #2291 : Act Math

Solve for 

.

Round to the nearest hundredth.

Possible Answers:

Correct answer:

Explanation:

To solve an exponential equation like this, you need to use logarithms.  This can be translated into:

Now, remember that your calculator needs to have this translated.  The logarithm  is equal to the following:

, which equals approximately .

Remember that you have the equation:

Thus, .

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