Math+magic

Here, I'll put directions for our weekly "Monday Math Magic" tricks.

1.1. 1. Write down a three digit number that is not a palindrome. 2.Find the difference between that number and its reverse. 3.Add this new number and its reverse. (If your new number is a two digit number, add a 0 at the beginning.) 4.Your result will be…drum roll please…. 1089!

1. Have your volunteer choose a three or four digit number and write it down. 2. Have them write another new number using all the same digits. 3. Tell them to subtract the two numbers. 4. The answer they get will be a multiple of nine. Have them tell you all but one of digits of their answer and you will be able to name the last because you remember that the sum of the digits of a multiple of 9 is always a multiple of 9. Examples: If the first three digits of their answer were 1, 4, and 3, the last digit would be a 1 because 1+4+3+1 = 9. If the first three digits of their answer were 5, 6, and 4, the last digit would be 3 because 5 + 6 + 4 + 3 = 18.

The Amazing Envelope Trick 1) Write a number between 1-50 on a piece of paper and put it in an envelope or write it on a paper and set it aside. 2) Have a volunteer choose a number between 50 and 99 and keep it a secret. 3) Have him add to his number. (The number you put in the blank should be 99 - your envelope number). 4) Tell your volunteer, "Remove the hundreds digit from the number you have now. Add it to the two digits you have left." 5) Tell your volunteer, "Now subtract that result from the number you originally chose." 6) Reveal what's in the envelope. It should match the result of your volunteer's last step.

1) Have your volunteer choose a whole number between 10 and 99. 2) Tell him or her to add 90 to the number they picked. 3) Have him or her remove the leftmost digit (the hundreds digit) and put it under what's left after the hundreds digit has been removed, then tell him to add those two numbers. 4) Ask for the number. In your head, add 9 (think +10 then -1) to their number to get their original number again!

 ** The twenty objects trick ** 1. Give your volunteer 20 pencils. Have him or her remove between 1 and 10 of the pencils. 2. Have your volunteer count the number of objects that are left in his hand and write that number somewhere you can't see it. 3. Have them add the digits of that number and record that number underneath it. 4. Tell your volunteer to take that number of objects (the last one they recorded) from their pile and set them aside. //Note to the magician: At this point there are 9 objects left in your volunteers hand.// 5. Ask your volunteer to give you a few of the objects left in his or her hand. Subtract that number from 9 in your head. 6. Announce the number of objects left in your volunteer's hand.