二十進制是底數為20的記數系統。瑪雅文明的瑪雅數字、因努伊特的卡克托維克數字即採用二十進制。
在二十進制中,使用20個數碼;大於9小於19的數碼,一般借鑑計算機中十六進制的表示法,使用字母「A-J」;即為「0、1、2、3、4、5、6、7、8、9、A、B、C、D、E、F、G、H、I、J」。 所以18寫作I20,19寫作J20,20寫作1020。
由此,可以得到:
- 2020 代表十進制的40 {= (2 × 201 + (0 × 200)}
- DA20 代表十進制的270{= (13 × 201) + (10 × 200}
- 10020 代表十進制的400{= (1 × 202) + (0 × 201) + (0 × 200)}
二十進制乘法表
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
A |
B |
C |
D |
E |
F |
G |
H |
I |
J |
10
|
2
|
4 |
6 |
8 |
A |
C |
E |
G |
I |
10 |
12 |
14 |
16 |
18 |
1A |
1C |
1E |
1G |
1I |
20
|
3
|
6 |
9 |
C |
F |
I |
11 |
14 |
17 |
1A |
1D |
1G |
1J |
22 |
25 |
28 |
2B |
2E |
2H |
30
|
4
|
8 |
C |
G |
10 |
14 |
18 |
1C |
1G |
20 |
24 |
28 |
2C |
2G |
30 |
34 |
38 |
3C |
3G |
40
|
5
|
A |
F |
10 |
15 |
1A |
1F |
20 |
25 |
2A |
2F |
30 |
35 |
3A |
3F |
40 |
45 |
4A |
4F |
50
|
6
|
C |
I |
14 |
1A |
1G |
22 |
28 |
2E |
30 |
36 |
3C |
3I |
44 |
4A |
4G |
52 |
58 |
5E |
60
|
7
|
E |
11 |
18 |
1F |
22 |
29 |
2G |
33 |
3A |
3H |
44 |
4B |
4I |
55 |
5C |
5J |
66 |
6D |
70
|
8
|
G |
14 |
1C |
20 |
28 |
2G |
34 |
3C |
40 |
48 |
4G |
54 |
5C |
60 |
68 |
6G |
74 |
7C |
80
|
9
|
I |
17 |
1G |
25 |
2E |
33 |
3C |
41 |
4A |
4J |
58 |
5H |
66 |
6F |
74 |
7D |
82 |
8B |
90
|
A
|
10 |
1A |
20 |
2A |
30 |
3A |
40 |
4A |
50 |
5A |
60 |
6A |
70 |
7A |
80 |
8A |
90 |
9A |
A0
|
B
|
12 |
1D |
24 |
2F |
36 |
3H |
48 |
4J |
5A |
61 |
6C |
73 |
7E |
85 |
8G |
97 |
9I |
A9 |
B0
|
C
|
14 |
1G |
28 |
30 |
3C |
44 |
4G |
58 |
60 |
6C |
74 |
7G |
88 |
90 |
9C |
A4 |
AG |
B8 |
C0
|
D
|
16 |
1J |
2C |
35 |
3I |
4B |
54 |
5H |
6A |
73 |
7G |
89 |
92 |
9F |
A8 |
B1 |
BE |
C7 |
D0
|
E
|
18 |
22 |
2G |
3A |
44 |
4I |
5C |
66 |
70 |
7E |
88 |
92 |
9G |
AA |
B4 |
BI |
CC |
D6 |
E0
|
F
|
1A |
25 |
30 |
3F |
4A |
55 |
60 |
6F |
7A |
85 |
90 |
9F |
AA |
B5 |
C0 |
CF |
DA |
E5 |
F0
|
G
|
1C |
28 |
34 |
40 |
4G |
5C |
68 |
74 |
80 |
8G |
9C |
A8 |
B4 |
C0 |
CG |
DC |
E8 |
F4 |
G0
|
H
|
1E |
2B |
38 |
45 |
52 |
5J |
6G |
7D |
8A |
97 |
A4 |
B1 |
BI |
CF |
DC |
E9 |
F6 |
G3 |
H0
|
I
|
1G |
2E |
3C |
4A |
58 |
66 |
74 |
82 |
90 |
9I |
AG |
BE |
CC |
DA |
E8 |
F6 |
G4 |
H2 |
I0
|
J
|
1I |
2H |
3G |
4F |
5E |
6D |
7C |
8B |
9A |
A9 |
B8 |
C7 |
D6 |
E5 |
F4 |
G3 |
H2 |
I1 |
J0
|
10
|
20 |
30 |
40 |
50 |
60 |
70 |
80 |
90 |
A0 |
B0 |
C0 |
D0 |
E0 |
F0 |
G0 |
H0 |
I0 |
J0 |
100
|
轉換
(Dec)十進
|
(Vig)二十進
|
1
|
1
|
2
|
2
|
3
|
3
|
4
|
4
|
5
|
5
|
6
|
6
|
7
|
7
|
8
|
8
|
9
|
9
|
10
|
A
|
11
|
B
|
12
|
C
|
13
|
D
|
14
|
E
|
15
|
F
|
16
|
G
|
17
|
H
|
18
|
I
|
19
|
J
|
20
|
10
|
21
|
11
|
22
|
12
|
23
|
13
|
24
|
14
|
25
|
15
|
26
|
16
|
27
|
17
|
28
|
18
|
29
|
19
|
30
|
1A
|
31
|
1B
|
32
|
1C
|
33
|
1D
|
34
|
1E
|
35
|
1F
|
36
|
1G
|
37
|
1H
|
38
|
1I
|
39
|
1J
|
40
|
20
|