Math Magic
THE NINE MACHINE:
Here is a unique way to work out the 9th table of multiplication for amateurs.
Preparation:
Hold your hands in front of you with your fingers straight out. Imagine a number for each of your fingers from left to right starting with 1 on the thumb of your left hand, 2 on the index of your left hand and so on. You will end with the number 10 on your right thumb.
Procedure:
Now you can multiply nine times any number from 1 to 10.
Here is an example:
To multiply 9x2 bend the number 2 finger (the index on your left hand). Now, count how many fingers are on each side of it. There will be one finger on the left and eight fingers on the right.
1 next to 8 gives the number ‘18’. There’s the answer.
Try the same for multiplication of 9 using different numbers from 1 to 10.
MULTIPLICATION WING:
You show your spectator a huge number. Your spectator thinks up any single digit number and tells it to you. You have them multiply the huge number by another different number by another different number, and the final answer is a row of digits identical to the one they thought of at the beginning.
Procedure:
1. Write down the huge number: “ 1 2 3 4 5 6 7 8 9”
2. Now ask your spectator to tell you any single digit number (1 to 9). To yourself, multiply this number by 9 and write the answer down under the ‘huge’ number.
3. Have your spectator multiply by the huge number by the one you just wrote down.
Here is an example:
Suppose your spectator chooses the number 7.
Now you multiply 7x9=63.
Now you multiply the huge number 123456789 by 63 i.e.,
123456789
X 63
----------------
7777777707
---
Hence the last two digits denote your spectator’s chosen number.
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