The materials you need for this math trick is :
1. A paper with a clock image on it. (The clock you have in your classroom with an hour hand, minute hand and second hand is the type of image you want).
2. A pencil.
Here's what you do :
1. Ask your friend to come up with any hour on the clock without telling you. Tell him when you do get his/her number, he/she should say stop.
2. Tell him or her that you will point randomly on the clock to different numbers as he/she silently counts up to 20. (FROM HIS/HER CHOSEN NUMBER).
3. Inform him that he must start at the hour he/she chose, and start adding 1 hour everytime you point to a random number.
4. When he/she finally counts up to 20, he/she will say stop. Your pencil should be pointing to the number he/she chose.
How things work :
1. When your friend is counting up to 20 from the number he chose (or time in this case), you too should be counting up to 20 too but you start at 1 and continue on.
2. The first 7 numbers you point at randomly, must not be 12 but could be anything else.
3. The eight number you point towards, MUST be 12.
4. Now continue around the clock BACKWARDS until your friend tells you to stop.
Example :
If he/she says 8:00. He/she should count 9:00 when you point to your first number. He/she should count to 10:00 on the second number. Etc...
This example was taken by :
http://www.geocities.com/EnchantedForest/Tower/1133/timewill.htm.
I tried my best to put it into my own words, hope it's understandable. =T If not, view the site.
Welcome to a world where creativity, ingenuity, and mathematics mesh together to create Grade 10 Precalculus math.
