[Mental Math]

The Fibonacci numbers are a series of whole numbers in which each number is the sum of the two preceding numbers. Beginning with 0 and 1, the sequence of Fibonacci numbers would be 0,1,1, 2, 3, 5, 8, 13, 21 etc. The Fibonacci Number Tricks amazes almost everyone. For more click here

Fibonacci Addition Trick

Step 1: Choose two numbers Step 2: Form a Fibonacci sequence for ten numbers
Example, Let us choose number 5 for the first number and 6 for the second number. Then add the numbers to get a Fibonacci sequence. 5+6 gives the 3rd number which is 11; 6+11 gives the 4th number which is 17. The entire sequence is as follows: 1st - 5
2nd - 6
3rd - 11
4th - 17
5th - 28
6th - 45
7th - 73
8th - 118
9th - 191
10th - 309 The trick is to ... multiply the 7th number by 11 (you always multiply it by 11). The answer you get when you multiply the 7thnumber by 11 will always be the same result as if you had added all ten numbers. In the above example, the 7th number is 73. Multiply 73 by 11 and the answer is 803. If you add all 10 numbers together the answer will also be 803.

Now, you can amaze your friends and family members by telling them the sum of 10 Fibonacci numbers orally.
First, tell them to take a Fibonacci sequence of 10 numbers (as above) behind you. This needs them to write down the numbers sequentially. Now, tell them to let you look the sequence for once and you notice the 7th number and you can easily tell them the sum of those 10 numbers orally simply by multiplying the 7^th number by 11 mentally. And you know the technique to multiply any number by 11 mentally. So, it's just a matter of blink of eyes!
Try this with your own numbers.

[Tres Juicy]

Nice link