1. The Famous Mystery Calculator Trick
Ask your friend to choose a number [1-63].
Show them each card here in turn and ask them if their number appears on it.
You can guess the number by adding the top left corner numbers of each card that has their number.
Can you find the trick?
The first hint is if you have one more card, your friend can pick a number [1 - 127]
Can you guess it now?
Another hint is 1 appears only on the first of the cards and 63 appears on them all.
... Yes, It is the Binary way of writing the number - each card is the binary digit represented by the top left corner number. (Cards are not in exact order to create the mystery!)
63 = (1 + 4 + 16 + 2 + 8 + 32) 1 1 1 1 1 1 (in all 6 cards)
23 = (1 + 4 +16 + 2) so only in first four cards.