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# The binary number 10101 is equivalent to the decimal number 21

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## The Binary Number 10101 and Its Equivalent in Decimal

SMART WORLD - Binary numbers are a system of representing values using only two digits, 0 and 1. These digits are known as "bits," and a group of eight bits is called a "byte." Binary numbers are used in many different fields, including computer science and engineering, as they provide a simple and efficient way to represent and manipulate data.

In this article, we will explore the specific case of the binary number 10101 and how it relates to the decimal number system, which is the system most commonly used in everyday life. The decimal number system is based on the number 10 and uses the digits 0 through 9 to represent values. We will see how the binary number 10101 can be converted to its equivalent in decimal, and discuss some of the applications of this conversion.

### Basics of Binary Numbers

In the binary number system, each digit is referred to as a "bit," and each bit has a place value depending on its position in the number. The rightmost bit is the least significant bit (LSB), and each successive bit to the left is worth twice as much as the previous one. This system is known as base 2, as it uses only two digits (0 and 1) to represent values.

#### For example, the binary number 1001 can be written as:

1 x 2^3 + 0 x 2^2 + 0 x 2^1 + 1 x 2^0

= 8 + 0 + 0 + 1

= 9

So, the binary number 1001 is equivalent to the decimal number 9.

To convert a binary number to decimal, we simply calculate the sum of the place values for each 1 in the binary number. For example, to convert the binary number 10101 to decimal, we would calculate:

1 x 2^4 + 0 x 2^3 + 1 x 2^2 + 0 x 2^1 + 1 x 2^0

= 16 + 0 + 4 + 0 + 1

= 21

### Conversion of Binary Number 10101 to Decimal

Now that we understand the basics of binary numbers and how to convert them to decimal, let's apply this process to the specific case of the binary number 10101. As we saw above, the place values for each bit in this number are 16, 8, 4, 2, and 1, from left to right. Since the first, third, and fifth bits are 1, we will include their corresponding place values in our sum. Therefore, the decimal equivalent of the binary number 10101 is:

1 x 2^4 + 0 x 2^3 + 1 x 2^2 + 0 x 2^1 + 1 x 2^0

= 16 + 0 + 4 + 0 + 1

= 21

### Applications of Binary-Decimal Conversion

Understanding the relationship between binary and decimal numbers is important in a number of fields, particularly in computer science and engineering. Computer systems often use binary to represent and manipulate data, as it is a simple and efficient way to store and process information. Therefore, being able to convert between binary and decimal is a fundamental skill for anyone working with computers.

In addition to computer science, binary numbers are used in a variety of other industries and applications. For example, they are used in telecommunications to represent the two states of an electrical signal (on or off), and in electronic circuits to represent the two possible states of a switch (open or closed).

## Conclusion

In this article, we have seen how the binary number 10101 can be converted to its equivalent in decimal, 21. We have explored the basics of binary numbers and how they differ from decimal numbers, and we have discussed some of the practical applications of understanding the relationship between these two systems.

Understanding binary and decimal numbers and how they are used in the world around us is an important skill that can be useful in a variety of fields and contexts. We encourage readers to continue learning about these systems and how they are used in the world today.

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