Shuffle a deck of 52 cards.
Ask 2 participants to each take one small pile of cards.
You will keep the remainder of the cards in one pile.

Ask the participants to total the number of cards they each have in their small pile of cards.

While participants count their cards, total your number of cards and subtract this total from either 7 or 16.

If your total is less than 7, subtract your total from 7
If your total is more than 7 subtract your total from 16.

In the video, I have 12 cards in my stack.
Therefore 16 - 12 = 4

Find a 4 in your pile of cards and place it face down on the table.

Participants count their cards.

If their cards total a two digit number, add these numbers together.

In the video, one participant has 21 cards (2+1=3)
The othe participant has 19 cards (9+1 = 10  then 1+0 =1)

Add these two digits : 3 + 1 = 4

Turn over your prediction card.

Magic!

Watch the video.