Algebra II : Number Theory

Study concepts, example questions & explanations for Algebra II

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Example Questions

Example Question #71 : Number Theory

Which of the following is an irrational number?  

Possible Answers:

Correct answer:

Explanation:

An irrational number is a number that cannot be rewritten as a ratio of two numbers such as  or  since their decimal numbers are continuous.  

Square roots that are not perfect squares are irrational such as:

Be careful with numbers that are fixed.    Fixed numbers are finite and can be rewritten as a fractional term.

Imaginary numbers are neither irrational or real numbers and is defined as the term .  The value of  is an imaginary number.  These are called complex numbers.

Percentages can be rewritten as a fraction.

The answer is:  

Example Question #5121 : Algebra Ii

Try without a calculator.

True or false: the set 

comprises only irrational numbers.

Possible Answers:

True

False

Correct answer:

False

Explanation:

The square root of an integer is rational if and only if the integer is a perfect square of another integer.

,

so 16 is a perfect square, and  is a rational number. The statement is therefore false.

Example Question #5122 : Algebra Ii

Try without a calculator.

True or false: the set 

comprises only irrational numbers.

Possible Answers:

True

False

Correct answer:

True

Explanation:

  is an irrational number, as is any integer multiple of . All of the elements are integer multiples of , so all of them are irrational.

Example Question #5123 : Algebra Ii

Try without a calculator.

True or false: the set 

comprises only irrational numbers.

Possible Answers:

True

False

Correct answer:

True

Explanation:

 is an irrational number, as is any integer multiple of . All of the elements are integer multiples of , so all of them are irrational.

Example Question #75 : Number Theory

Which of the following represents an irrational number?

Possible Answers:

None of the numbers is irrational.

Correct answer:

Explanation:

First, recall the definition of irrational numbers. Irrational numbers cannot be expressed as a ratio of integers.

The answer  is incorrect because it is a repeating decimal that can be rewritten as the following fraction:

 

In a similar vein, the following choice is already written as a simple fraction (negative numbers are not irrational):

It is important to note that not all square roots are irrational. For instance, the following square root can be simplified quite easily:

 

The only answer that cannot be expressed as a simple fraction is:  

The answer is:  

Example Question #1 : Irrational Numbers

Which of the following is an irrational number?

Possible Answers:

Correct answer:

Explanation:

A rational number can be expressed as a fraction of integers, while an irrational number cannot.  

can be written as .   

 is simply , which is a rational number.  

The number  can be rewritten as a fraction of whole numbers, , which makes it a rational number.  

is also a rational number because it is a ratio of whole numbers.  

The number, , on the other hand, is irrational, since it has an irregular sequence of numbers (...) that cannot be written as a fraction.

Example Question #1 : Number Sets

If , , and , then find the following set:

 

Possible Answers:

Correct answer:

Explanation:

The union is the set that contains all the numbers from  and .  Therefore the union is

 

Example Question #2 : Number Sets

If , , and , find the following set:

 

Possible Answers:

Correct answer:

Explanation:

The intersection is the set that contains only the numbers found in all three sets. Therefore the intersection is .

Example Question #1 : Number Sets

If , , and , find the following set:

 

Possible Answers:

Correct answer:

Explanation:

The intersection is the set that contains the numbers that appear in both  and .  Therefore the intersection is .

Example Question #4 : Number Sets

If , , and , find the following set:

 

Possible Answers:

Correct answer:

Explanation:

The intersection is the set that contains the numbers found in both sets. Therefore the intersection is .

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