While your back is turned, a spectator arranges the pictures of birds in any way desired. As soon as you turn around, you can instantly and accurately state the number of birds showing. Finally, you can instantly state the number of birds, even after the cards are shut tightly inside a case!!
You explain that your new hobby birdwatching. With unbelievable speed, you demonstrate your ability to count how many birds are showing.
Finally, you demonstrate your ability to divine how many birds are inside of a closed case, without looking. Your audience will be taken aback by your super-human skill.

Quantity: