Start with all fingers down.
ooooo This is zero.
Put your index finger up.
o1ooo This is one. You probably already knew that and have been doing this since before you could speak in sentences. But unlike your grade school counting method that only reaches 10, we will make one small modification to reach 99! So let's get on with the parts we already know:
And stop. Normally, we would keep going onto the next hand, but let's keep this hand counting by putting fingers down in the same order we put them up. So, from all five fingers up:
Put your index finger down.
1o111 This is six.
Put your middle finger down.
1oo11 This is seven.
Put your ring finger down.
1ooo1 This is eight.
Put your pinky down (only your thumb should be extended now).
Hopefully you've gotten the pattern. Now you can start using your left hand for the tens digit.
Put your index finger up on your left hand and put your thumb back down on your right hand.
ooooo This is ten.
And with just two hands and a simple counting strategy we can represent any number from 0 to 99!
o11ooall fingers (but not thumb) up on left hand; index and middle finger up on right hand.
1oooomiddle, ring, pinky fingers and thumb up on left hand; only thumb up on right hand.
1oo11ring finger, pinky finger, and thumb up on both right and left hands.