This is a good self working card trick I find very useful when a spectator makes it impossible for you to do a trick. I call the trick, Mathomatic.
Also to remember the suit of the card.
Tell them to double the value of the card.
Then tell them to add three to the total.
Then tell them to multiply the complete total by five.
This done ask them to concentrate on the suit.
If the card is a diamond they must add one.
If the card is a club they must add two.
If the card is a heart they must add three.
If the card is a spade they must add four.
They must then tell you the final total.
From this total, you immediately know the chosen card.
The Secret: Is to mentally subtract 15 from the given total. You will have a number of two figures, possibly three
The last figure gives you the suit (diamonds 1, clubs 2, hearts 3, spades 4.) while the first figure gives you the suit.
Example: Jack of clubs
11 doubled is 22, add 3--25, multiply by 5--125. add for clubs--makes 127. You are told that number.
Subtract 15 mentally. Result 112. Last figure (2) means clubs, first figure(11) means Jack.