This is more of a joke than a trick, yet it really mystifies many people. Tell the group that you have 11 fingers, counting your thumbs (Father could count while child holds up hands.)
Using your right forefinger as a pointer touch each finger of the left hand, counting "one, two, three, four, five."
Then your left forefinger counts the right fingers: "Six, seven, eight, nine, ten." "Strange," you say, "I thought I had eleven. Let's try again."
You start counting backwards, pointing to the fingers of the right hand. "Ten, nine, eight, seven, six," then stop, hold up your left hand and say: "And five are eleven!"
Executed rapidly, this clever method of counting is very deceptive.