The magician asked the audience to fiddle with a pile of paper and got two numbers, and miraculously, the magician's notepad seemed to have foreseen them early on.
On weekends, dad didn't read the newspaper and drink tea as usual, but cut a large cardboard into 8 small cards, and took a marker pen and wrote large numbers on the front and back of these cards.
"Dad, are you going to perform mathematical magic?" The bunny saw it, put down the toy in his hand and walked over to ask.
"It's so clever." Dad said approvingly, folding the cards in his hand and folding them, then dividing them into two piles like playing cards, and letting the bunny choose one of them.
The bunny casually ordered the pile on the right-hand side, so Dad picked them up and divided them into two groups like a card, each with two cards. Dad asked the bunny to choose one of the groups again, and the bunny quickly chose it. Dad asked The Bunny to add up the numbers on the two sets of cards he chose and write them on the paper, and then picked a random card to turn over. Bunny saw that the numbers on the card were 1 and 8, adding up to 9, so she wrote a 9 on the paper.
"You pick one of the cards and turn it over." Dad said. The bunny turned over the card with the number 8 written on it, and the number on the back was 11. "Now, add up the numbers on those two cards." Dad said again. The bunny quickly added, it was 12.
"But what do these 9s and 12s mean?" Bunny asked Daddy. Dad smiled and took out a notepad and handed it to Xiao Wei, and Xiao Bunny looked at it, it was the 2011 annual calendar notepad. As soon as the bunny opened the notepad, a small piece of paper fell out, which said September 12, and a picture of a full moon.
"It turned out to be the Mid-Autumn Festival!" Bunny said happily, but she wondered, how did Notepad know that I would draw these two numbers?
Magic revealed
Props: 8 pieces of cardboard, an annual calendar notebook
Get ready
Write 1 on one side of the first cardboard and 4 on the other; 2 and 5 in the second; 3 and 6 in the third; 4 and 7 in the fourth; 5 and 8 in the fifth; 6 and 9 in the sixth; 7 and 10 in the seventh; and 8 and 11 in the eighth.
The performance process
(1) The magician shows the audience 8 pieces of cardboard prepared, which are marked with the numbers 1 to 8 on one side and 4 to 11 on the other. The magician stacks these cards (the side with 1 to 8 written on it is facing up, in order 1, 2, 3, 4, 8, 7, 6, 5) from bottom to top) and divides them into two piles like a card. Then ask the audience to choose one of them.
(2) Take the stack of cards selected by the audience in your hand, divide them into two piles like a card, and ask the audience to choose one of them again. At this point we will get two cards, and the magician adds up the two numbers on the card and tells the audience that it is 9.
(3) Ask the audience to pick a card at random and turn it over. Add the two numbers shown and you get 12. Pretend not to know what the connection between these two numbers is, and then suddenly feel the almanac notepad and ask the audience to open it. When the audience opens, they will find that September 12 is the Mid-Autumn Festival in 2011, and the audience is also surprised to find that a card "Spend a good full moon" is added to the notepad.
Highlights
Note that after showing the card to the audience, be sure to stack the cards in order.
Mathematical principles
This seemingly random set of numbers is actually carefully designed, and through the specified arrangement, the numbers 9 and 12 can always be obtained. You can also try to change these two numbers to design more interesting magic tricks. For example, if the numbers on the front and back of the card are 1 to 8 and 9 to 16, respectively, then you will end up with the numbers 9 and 17, and you can find the pattern after a few more attempts.