The binary system (1900 AD)

Each number is represented by multiples of 2.

Only the symbols 0 and 1 are used.

0
1
2
3
4
5
6
 
1 x 1
1 x 2 + 0 x 1
1 x 2 + 1 x 1
1 x 4 + 0 x 2 + 0 x 1
1 x 4 + 0 x 2 + 1 x 1
1 x 4 + 1 x 2 + 0 x 1
0
1
10
11
100
101
110


What do these binary numbers represent?                                          1000 
1010
11111
1001111