LSC1: NUMBER BASES

NUMBER BASES

Sub-topic 1: Representing Numbers in Different

Bases on the Abacus

Decimal to Other Bases

Converting a decimal number to other base numbers is easy. We have to divide the decimal number by the converted value of the new base.

Decimal to Binary Number:

Suppose if we have to convert decimal to binary, then divide the decimal number by 2.

Example 1. Convert (25)₁₀ to binary number.

Solution: Let us create a table based on this question.

Therefore, from the above table, we can write,

(25)₁₀ = (11001)₂

Decimal to Octal Number:

To convert decimal to octal number we have to divide the given original number by 8 such that base 10 changes to base 8. Let us understand with the help of an example.

Example 2: Convert 128₁₀ to octal number.

Solution: Let us represent the conversion in tabular form.

Therefore, the equivalent octal number = 200₈

Decimal to Hexadecimal:

Again in decimal to hex conversion, we have to divide the given decimal number by 16.

Example 3: Convert  128₁₀ to hex.

Solution: As per the method, we can create a table;

Therefore, the equivalent hexadecimal number is 80₁₆

Here MSB stands for a Most significant bit and LSB stands for a least significant bit.

Other Base System to Decimal Conversion

Binary to Decimal:

In this conversion, binary number to a decimal number, we use multiplication method, in such a way that, if a number with base n has to be converted into a number with base 10, then each digit of the given number is multiplied from MSB to LSB with reducing the power of the base. Let us understand this conversion with the help of an example.

Example 1. Convert (1101)₂ into a decimal number.

Solution: Given a binary number (1101)₂.

Now, multiplying each digit from MSB to LSB with reducing the power of the base number 2.

1 × 2³ + 1 × 2² + 0 × 2¹ + 1 × 2⁰

= 8 + 4 + 0 + 1

= 13

Therefore, (1101)₂ = (13)₁₀

Octal to Decimal:

To convert octal to decimal, we multiply the digits of octal number with decreasing power of the base number 8, starting from MSB to LSB and then add them all together.

Example 2: Convert 22₈ to decimal number.

Solution: Given, 22₈

2 x 8¹ + 2 x 8⁰

= 16 + 2

= 18

Therefore, 22₈ = 18₁₀

Hexadecimal to Decimal:

Example 3: Convert 121₁₆ to decimal number.

Solution: 1 x 16² + 2 x 16¹  + 1 x 16⁰

= 16 x 16 + 2 x 16 + 1 x 1

= 289

Therefore, 121₁₆ = 289₁₀

Hexadecimal to Binary Shortcut Method

To convert hexadecimal numbers to binary and vice versa is easy, you just have to memorize the table given below.

You can easily solve the problems based on hexadecimal and binary conversions with the help of this table. Let us take an example.

Example: Convert (89)₁₆ into a binary number.

Solution: From the table, we can get the binary value of 8 and 9, hexadecimal base numbers.

8 = 1000 and 9 = 1001

Therefore, (89)₁₆ = (10001001)₂

Octal to Binary Shortcut Method

To convert octal to binary number, we can simply use the table. Just like having a table for hexadecimal and its equivalent binary, in the same way, we have a table for octal and its equivalent binary number.

Example: Convert (214)₈ into a binary number.

Solution: From the table, we know,

2 → 010

1 → 001

4 → 100

Therefore,(214)₈ = (010001100)₂