 ## Decimal number

Decimal number is system number who have 10 digit numbers, consist of 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9. Decimal number base 10 numeral system, and it's the most used in the system numbers.

Decimal number weights
100 = 1 → first digit, weights one
101 = 10 → second digit, weights ten
102 = 100 → third digit, weights hundred
103 = 1000 → fourth digit, weights thousand
104 = 1000 → fifth digit, weights ten thousand
etc.

Example 1:
Describe a decimal number 2015 in the system numbers

Completion:
2015 (10) =
5 → 5 × 100 = 5
1 → 1 × 101 = 10
0 → 0 × 102 = 0
2 → 2 × 103 = 2000
2015 → 5 + 10 + 0 + 2000 = 2015

Example 2:
Describe a decimal number 1000518 in the system numbers

Completion:
1000518 (10) =
8 → 8 × 100 = 8
1 → 1 × 101 = 10
5 → 5 × 102 = 500
0 → 0 × 103 = 0
0 → 0 × 104 = 0
0 → 0 × 105 = 0
1 → 1 × 106 = 1000000
1000518 → 8 + 10 + 500 + 0 + 0 + 0 + 1000000 = 1000518.

## Binary number

Binary number is system number who have 2 digit numbers, which is 0 and 1. Binary number base 2 numeral system.

Binary number weights
20 = 1 → first digit, weights one
21 = 2 → second digit, weights two
22 = 4 → third digit, weights four
23 = 8 → fourth digit, weights eight
24 = 16 → fifth digit, weights sixteen
etc.

Example 1:
Convert binary number 110 to decimal number

Completion:
110 (2) = ? (10)
0 → 0 × 20 = 0
1 → 1 × 21 = 2
1 → 1 × 22 = 4
110 → 0 + 2 + 4 = 6
110 (2) = 6 (10)

Example 2:
Convert binary number 11010 to decimal number

Completion:
11010 (2) = ? (10)
0 → 0 × 20 = 0
1 → 1 × 21 = 2
0 → 0 × 22 = 0
1 → 1 × 23 = 8
1 → 1 × 24 = 16
11010 → 0 + 2 + 0 + 8 + 16 = 26
11010 (2) = 26 (10)