Binary Fingers!

Forget about counting to 10 on your fingers ... you can count past 1,000 if you want!

Right Hand

With just your right hand you can count to 31:

No fingers up is 0
Thumb is 1
Index finger is 2
2 and 1
makes 3
Middle finger is 4
Add your thumb
for 5
4 and
2 makes 6
4 and 2 and 1
makes 7

Fourth finger is 8

... and continue the pattern:

  • add your thumb (+1) to make 9,
  • or add your index finger (+2) to make 10
  • or add thumb (+1) and index finger (+2) to make 11
  • etc.

In fact you are counting in Binary:

Number Made by
1 1         up
2 2       up  
3 2+1       up up
4 4     up    
5 4+1     up   up
6 4+2     up up  
7 4+2+1     up up up
8 8   up      
9 8+1   up     up
10 8+2   up   up  
11 8+2+1   up   up up
12 8+4   up up    
13 8+4+1   up up   up
14 8+4+2   up up up  
15 8+4+2+1   up up up up
16 16 up        
17 16+1 up       up
  etc....          

Here are some more examples:

16+8+2
makes 26
16+8+4+2
makes 30

 

 

 

 

Your Turn

Practice counting from 0 to 31 on your fingers, just like above.

Do it many times until it becomes easy.

When you can do it well, demonstrate it to your teacher or a friend.

Left Hand

Want bigger numbers? Your left hand can help:

Now we can use all 10 fingers to make numbers like these:

32+2
makes 34
32+16+8+4
makes 60
512+256+32+2+1
makes 803

And lastly, what happens when all fingers are up?

512+256+128+64+32+16+8+4+2+1
makes 1,023

So now you can count just past 1,000 using only 10 fingers. Wow.

Practice this over the next few days ... you will gain a new skill and also find binary much easier to understand.