Showing that a Decimal is a Rational Number

Oct 13, 2025 by wbrum.org 132 views

Introduction

In mathematics, numbers can be classified into two main categories: rational and irrational. Rational numbers are those that can be expressed as the ratio of two integers, while irrational numbers cannot be expressed in this way. In this article, we will explore the concept of rational numbers and demonstrate how to show that a given decimal is a rational number. We will also determine the range of integers between which a given square root lies.

What are Rational Numbers?

Rational numbers are those that can be expressed as the ratio of two integers, i.e., in the form a/b, where a and b are integers and b is non-zero. For example, 3/4, 22/7, and 1/2 are all rational numbers. Rational numbers can also be expressed as decimals, and in this case, the decimal representation is either a finite or repeating decimal.

Showing that a Decimal is a Rational Number

To show that a decimal is a rational number, we need to express it as the ratio of two integers. Let's consider the decimal 3,218. We can express this decimal as a fraction by dividing it by 1,000,000, which is the number of digits in the decimal.

3,218 ÷ 1,000,000 = 3.218

We can simplify this fraction by dividing both the numerator and the denominator by their greatest common divisor, which is 1.

3.218 = 3218/1000

Therefore, the decimal 3,218 can be expressed as the ratio of two integers, 3218 and 1000, and is therefore a rational number.

Determining the Range of Integers for a Square Root

Now, let's consider the square root of 30. We need to determine the range of integers between which this square root lies. To do this, we can use the fact that the square root of a number is always greater than or equal to the number itself and less than or equal to the next integer.

Step 1: Find the Square Root of 30

The square root of 30 is approximately 5.48.

Step 2: Determine the Range of Integers

Since the square root of 30 is approximately 5.48, we know that it lies between the integers 5 and 6.

Conclusion

In this article, we have demonstrated how to show that a decimal is a rational number and determined the range of integers between which a given square root lies. We have also explored the concept of rational numbers and their properties.

Expanding and Simplifying Algebraic Expressions

Now, let's consider the algebraic expression (a-2)^2 - a(a+4). We need to expand and simplify this expression.

(a-2)^2 - a(a+4)

To expand and simplify this expression, we can use the distributive property and the formula for the square of a binomial.

(a-2)^2 - a(a+4) = (a^2 - 4a + 4) - a^2 - 4a = -4a + 4 - a^2 - 4a = -8a + 4 - a^2

Therefore, the expanded and simplified form of the expression is -8a + 4 - a^2.

Conclusion

In this article, we have demonstrated how to expand and simplify algebraic expressions and determined the range of integers between which a given square root lies. We have also explored the concept of rational numbers and their properties.

Final Thoughts

Introduction

In our previous article, we explored the concept of rational numbers and demonstrated how to show that a decimal is a rational number. We also determined the range of integers between which a given square root lies. In this article, we will answer some frequently asked questions about rational and irrational numbers.

Q&A

Q: What is the difference between a rational number and an irrational number?

A: A rational number is a number that can be expressed as the ratio of two integers, i.e., in the form a/b, where a and b are integers and b is non-zero. An irrational number, on the other hand, is a number that cannot be expressed in this way.

Q: Can all rational numbers be expressed as decimals?

A: Yes, all rational numbers can be expressed as decimals. In fact, rational numbers can be expressed as either finite or repeating decimals.

Q: Can all irrational numbers be expressed as decimals?

A: No, not all irrational numbers can be expressed as decimals. In fact, most irrational numbers cannot be expressed as decimals.

Q: How do I determine if a number is rational or irrational?

A: To determine if a number is rational or irrational, you can try to express it as the ratio of two integers. If you can do this, then the number is rational. If you cannot do this, then the number is irrational.

Q: Can I use a calculator to determine if a number is rational or irrational?

A: Yes, you can use a calculator to determine if a number is rational or irrational. However, keep in mind that calculators can only give you an approximation of the number, and may not be able to determine if the number is rational or irrational.

Q: What is the significance of rational numbers in mathematics?

A: Rational numbers are significant in mathematics because they can be used to represent fractions and proportions. They are also used in many mathematical formulas and equations.

Q: What is the significance of irrational numbers in mathematics?

A: Irrational numbers are significant in mathematics because they can be used to represent quantities that cannot be expressed as fractions or proportions. They are also used in many mathematical formulas and equations.

Q: Can I use rational numbers to approximate irrational numbers?

A: Yes, you can use rational numbers to approximate irrational numbers. However, keep in mind that the approximation may not be exact, and may depend on the specific rational number used.

Q: Can I use irrational numbers to approximate rational numbers?

A: No, you cannot use irrational numbers to approximate rational numbers. Irrational numbers are not designed to approximate rational numbers, and may not be able to do so accurately.

Conclusion

In this article, we have answered some frequently asked questions about rational and irrational numbers. We have also explored the concept of rational numbers and their properties. Whether you are a student or a professional, understanding rational and irrational numbers is essential for success in mathematics.

Final Thoughts

In conclusion, rational numbers are those that can be expressed as the ratio of two integers, while irrational numbers cannot be expressed in this way. We have demonstrated how to show that a decimal is a rational number and determined the range of integers between which a given square root lies. We have also explored the concept of rational numbers and their properties. Whether you are a student or a professional, understanding rational and irrational numbers is essential for success in mathematics.

Additional Resources

For more information on rational and irrational numbers, please see the following resources:

Glossary

Rational Number: A number that can be expressed as the ratio of two integers, i.e., in the form a/b, where a and b are integers and b is non-zero.
Irrational Number: A number that cannot be expressed as the ratio of two integers.
Decimal: A number expressed in the form of a decimal point, e.g., 3.14.
Square Root: The number that, when multiplied by itself, gives a specified value, e.g., the square root of 16 is 4.