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March 3, 2015

March 3, 2015

Posted by **Jacob** on Saturday, April 7, 2012 at 3:47pm.

Discuss the basic mathematics behind the above magic effect. Discuss how the magician can quickly tell the sum of all the numbers before the participants are able to add them up. (

- calculus -
**Reiny**, Saturday, April 7, 2012 at 8:25pmlet the first two numbers written down be

x and y

the numbers would appear this way

x

y

x+y

x+2y

2x+3y

3x+5y

5x+8y

8x+13y

13x+21y

21x+34y , notice the "Fibonacci Number" pattern

total = 55x + 88y

= 11(5x + 8y)

The magician should be reasonably capable of doing some quick mental arithmetic

.... multiply the first number by 5 and the 2nd by 8, add those up, and multiply the result by 11

suppose the first 2 numbers written down are

4 and 7

5 times 4= 20, and 8 times 7 = 56

20+56 = 76

multiplying a two digit number by 11 is easy ...

11x76 = 836

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