## Hexa decimal number

Hexa decimal number is system number who have 16 digit numbers, which is 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E and F, where:
A present of 10
B present of 11
C present of 12
D present of 13
E present of 14
F present of 15.
Hexa decimal number base 16 numeral system.

Hexa decimal number weights
160 = 1 → first digit, weights one
161 = 16 → second digit, weights sixteen
162 = 256 → third digit, weights two hundred and six
163 = 4096 → fourth digit, weights 512
164 = 65536 → fifth digit, weights 4096
etc.

Example 1:
Convert Hexa decimal number 750 to decimal number

Completion:
750 (16) = ? (10)
0 → 0 × 160 = 0
5 → 5 × 161 = 80
7 → 7 × 162 = 7 × 256 = 1792
750 → 0 + 80 + 1792 = 1872
750 (16) = 1872 (10).

Example 2:
Convert Hexa decimal number 20BCA to decimal number

Completion:
20BCA (16) = ? (10)
A → 10 × 160 = 10
C → 12 × 161 = 192
B → 11 × 162 = 11 × 256 = 2816
0 → 0 × 163 = 0
2 → 2 × 164 = 2 × 65536 = 131072
20BCA → 10 + 192 + 2816 + 0 + 131072 = 134090
20BCA (16) = 134090 (10).

## Octal number

Octal number is system number who have 8 digit numbers, which is 0, 1, 2, 3, 4, 5, 6 and 7. Octal number base 8 numeral system.

Octal number weights
80 = 1 → first digit, weights one
81 = 8 → second digit, weights eight
82 = 64 → third digit, weights sixty four
83 = 512 → fourth digit, weights 512
84 = 4096 → fifth digit, weights 4096
etc.

Example 1:
Convert Octal number 370 to decimal number

Completion:
370 (8) = ? (10)
0 → 0 × 80 = 0
7 → 7 × 81 = 56
3 → 3 × 82 = 192
370 → 0 + 56 + 192 = 248
370 (8) = 248 (10)

Example 2:
Convert Octal number 55017 to decimal number

Completion:
55017 (8) = ? (10)
7 → 7 × 80 = 7
1 → 1 × 81 = 8
0 → 0 × 82 = 0
5 → 5 × 83 = 2560
5 → 5 × 84 = 20480
55017 → 7 + 8 + 0 + 2560 + 20480 = 23055
55017 (8) = 23055 (10)