81 in Binary

The process of converting 81 from decimal to binary involves dividing the number 81 by 2. Here, it is getting divided by 2 because the binary number system uses only 2 digits (0 and 1). The quotient becomes the dividend in the next step, and the process continues until the quotient becomes 0.

This is a commonly used method to convert 81 to binary. In the last step, the remainder is noted down bottom side up, and that becomes the converted value. For example, the remainders noted down after dividing 81 by 2 until getting 0 as the quotient is 1010001. Remember, the remainders here have been written upside down.

In the table shown below, the first column shows the binary digits (1 and 0) as 1010001. The second column represents the place values of each digit, and the third column is the value calculation, where the binary digits are multiplied by their corresponding place values.

The results of the third column can be added to cross-check if 1010001 in binary is indeed 81 in the decimal number system.

81 can be converted easily from decimal to binary. The methods mentioned below will help us convert the number. Let’s see how it is done.

Expansion Method: Let us see the step-by-step process of converting 81 using the expansion method.

Step 1 - Figure out the place values: In the binary system, each place value is a power of 2. Therefore, in the first step, we will ascertain the powers of 2.

2⁰ = 1

2¹ = 2

2² = 4

2³ = 8

2⁴ = 16

2⁵ = 32

2⁶ = 64

2⁷ = 128

Since 128 is greater than 81, we stop at 2⁶ = 64.

Step 2 - Identify the largest power of 2: In the previous step, we stopped at 2⁶ = 64. This is because in this step, we have to identify the largest power of 2, which is less than or equal to the given number, 81. Since 2⁶ is the number we are looking for, write 1 in the 2⁶ place. Now the value of 26, which is 64, is subtracted from 81. 81 - 64 = 17.

Step 3 - Identify the next largest power of 2: In this step, we need to find the largest power of 2 that fits into the result of the previous step, 17. So, the next largest power of 2 is 2⁴, which is less than or equal to 17. Now, we have to write 1 in the 2⁴ place. And then subtract 16 from 17. 17 - 16 = 1.

Step 4 - Identify the next largest power of 2: Now, we focus on 1. The largest power of 2 that fits into 1 is 2⁰. Write 1 in the 2⁰ place.

Step 5 - Identify the unused place values: In step 2, step 3, and step 4, we wrote 1 in the 2⁶, 2⁴, and 2⁰ places. Now, we can just write 0s in the remaining places, which are 2⁵, 2³, 2², and 2¹. Now, by substituting the values, we get, 1 in the 2⁰ place 0 in the 2¹ place 0 in the 2² place 0 in the 2³ place 1 in the 2⁴ place 0 in the 2⁵ place 1 in the 2⁶ place

Step 6 - Write the values in reverse order: We now write the numbers upside down to represent 81 in binary. Therefore, 1010001 is 81 in binary.

Grouping Method: In this method, we divide the number 81 by 2. Let us see the step-by-step conversion.

Step 1 - Divide the given number 81 by 2. 81 / 2 = 40. Here, 40 is the quotient and 1 is the remainder.

Step 2 - Divide the previous quotient (40) by 2. 40 / 2 = 20. Here, the quotient is 20 and the remainder is 0.

Step 3 - Repeat the previous step. 20 / 2 = 10. Now, the quotient is 10 and 0 is the remainder.

Step 4 - Repeat the previous step. 10 / 2 = 5. Here, the remainder is 0.

Step 5 - Repeat the previous step. 5 / 2 = 2. Here, the quotient is 2 and the remainder is 1.

Step 6 - Repeat the previous step. 2 / 2 = 1. Here, the remainder is 0.

Step 7 - Repeat the previous step. 1 / 2 = 0. Here, the remainder is 1. And we stop the division here because the quotient is 0.

Step 8 - Write down the remainders from bottom to top. Therefore, 81 (decimal) = 1010001 (binary).

There are certain rules to follow when converting any number to binary. Some of them are mentioned below:

Rule 1: Place Value Method

This is one of the most commonly used rules to convert any number to binary. The place value method is the same as the expansion method, where we need to find the largest power of 2. Let’s see a brief step-by-step explanation to understand the first rule. Find the largest power of 2 less than or equal to 81. Since the answer is 2⁶, write 1 next to this power of 2. Subtract the value (64) from 81. So, 81 - 64 = 17. Find the largest power of 2 less than or equal to 17. The answer is 2⁴. So, write 1 next to this power. Now, 17 - 16 = 1. Find the largest power of 2 less than or equal to 1. The answer is 2⁰. So, write 1 next to this power. Since there is no remainder, we can write 0 next to the remaining powers (2⁵, 2³, 2², and 2¹). Final conversion will be 1010001.

Rule 2: Division by 2 Method

The division by 2 method is the same as the grouping method. A brief step-by-step explanation is given below for better understanding. First, 81 is divided by 2 to get 40 as the quotient and 1 as the remainder. Now, 40 is divided by 2. Here, we will get 20 as the quotient and 0 as the remainder. Dividing 20 by 2, we get 10 as the quotient and 0 as the remainder. Divide 10 by 2 to get 5 as the quotient and 0 as the remainder. Divide 5 by 2 to get 2 as the quotient and 1 as the remainder. Divide 2 by 2 to get 1 as the quotient and 0 as the remainder. Divide 1 by 2 to get 0 as the quotient and 1 as the remainder. We stop the division once the quotient becomes 0. Now, we write the remainders upside down to get the binary equivalent of 81, 1010001.

Rule 3: Representation Method

This rule also involves breaking the number into powers of 2. Identify the powers of 2 and write them down in decreasing order, i.e., 2⁶, 2⁵, 2⁴, 2³, 2², 2¹, and 2⁰. Find the largest power that fits into 81. Repeat the process and allocate 1s and 0s to the suitable powers of 2. Combine the digits (0 and 1) to get the binary result.

Rule 4: Limitation Rule

The limitation of the binary system is that only 0s and 1s can be used to represent numbers. The system doesn’t use any other digits other than 0 and 1. This is a base 2 number system, where the binary places represent powers of 2. So, every digit is either a 0 or a 1. To convert 81, we use 0s for 2⁵, 2³, 2², and 2¹, and 1s for 2⁶, 2⁴, and 2⁰.

Learning a few tips and tricks is a great way to solve any mathematical problems easily. Let us take a look at some tips and tricks for binary numbers up to 81.

• Memorize to speed up conversions: We can memorize the binary forms for numbers 1 to 81.
   
• Recognize the patterns: There is a peculiar pattern when converting numbers from decimal to binary. 1 → 1 1 + 1 = 2 → 10 2 + 2 = 4 → 100 4 + 4 = 8 → 1000 8 + 8 = 16 → 10000 16 + 16 = 32 → 100000 32 + 32 = 64 → 1000000 64 + 17 = 81 → 1010001
   
• Even and odd rule: Whenever a number is even, its binary form will end in 0. For example, 10 is even and its binary form is 1010. Here, the binary of 10 ends in 0. If the number is odd, then its binary equivalent will end in 1. For example, the binary of 81 (an odd number) is 1010001. As you can see, the last digit here is 1.
   
• Cross-verify the answers: Once the conversion is done, we can cross-verify the answers by converting the number back to the decimal form. This will eliminate any unforeseen errors in conversion.
   
• Practice by using tables: Writing the decimal numbers and their binary equivalents on a table will help us remember the conversions.

• Decimal: It is the base 10 number system which uses digits from 0 to 9.

• Binary: This number system uses only 0 and 1. It is also called the base 2 number system.

• Place value: Every digit has a value based on its position in a given number. For example, in 102 (base 10), 1 has occupied the hundreds place, 0 is in the tens place, and 2 is in the ones place.

• Octal: It is the number system with a base of 8. It uses digits from 0 to 7.

• Power of 2: Refers to numbers that are the result of raising 2 to an exponent, used in the binary numbering system.